Filed Pursuant to Rule 424(b)(5)
Registration No. 333-223608

The information in this preliminary prospectus supplement and the accompanying prospectus is not complete and may be changed. This preliminary prospectus supplement and the accompanying prospectus are not an offer to sell these securities, and are not soliciting an offer to buy these securities, in any jurisdiction where the offer or sale is not permitted.

Subject to completion, dated April 26, 2018

PRELIMINARY PROSPECTUS SUPPLEMENT

(To prospectus dated March 12, 2018)

Capital One Financial Corporation

$             % Senior Notes Due 2021

$             % Senior Notes Due 2025

We will pay interest on the     % senior notes due 2021 (the “2021 fixed rate notes”) semi-annually in arrears on                 and                 of each year. We will make the first interest payment on the 2021 fixed rate notes on                 , 2018. The 2021 fixed rate notes will mature on                 , 2021.

We will pay interest on the     % senior notes due 2025 (the “2025 fixed rate notes” and, together with the 2021 fixed rate notes, the “notes”) semi-annually in arrears on                 and                 of each year. We will make the first interest payment on the 2025 fixed rate notes on                 , 2018. The 2025 fixed rate notes will mature on                 , 2025.

We have the option to redeem the 2021 fixed rate notes at a redemption price equal to 100% of the principal amount of the notes to be redeemed, plus accrued and unpaid interest thereon to the redemption date, in whole or in part at any time on or after                 , 2021 (which is the date that is one month prior to the maturity date of the 2021 fixed rate notes). See “Description of the Notes—Optional Redemption.”

We have the option to redeem the 2025 fixed rate notes at a redemption price equal to 100% of the principal amount of the notes to be redeemed, plus accrued and unpaid interest thereon to the redemption date, in whole or in part at any time on or after                 , 2025 (which is the date that is one month prior to the maturity date of the 2025 fixed rate notes). See “Description of the Notes—Optional Redemption.”

The notes will be our unsecured obligations and will rank equally with all of our existing and future unsecured and unsubordinated indebtedness that may be outstanding from time to time.

We will issue the notes in minimum denominations of $2,000 and integral multiples of $1,000 in excess thereof. There is no sinking fund for the notes. The notes are a new issue of securities with no established trading market. The notes will not be listed on any securities exchange.

Investing in the notes involves risks. See “Risk Factors” beginning on page S-4 of this prospectus supplement.

Neither the Securities and Exchange Commission (the “SEC”) nor any state securities commission has approved or disapproved of these securities or determined if this prospectus supplement or the accompanying prospectus is truthful or complete. Any representation to the contrary is a criminal offense.

The notes are not savings accounts, deposits or other obligations of a bank and are not insured or guaranteed by the Federal Deposit Insurance Corporation (the “FDIC”) or any other governmental agency or instrumentality.

The underwriters expect to deliver the notes in book-entry form only through the facilities of The Depository Trust Company and its participants, including Euroclear System and Clearstream Banking, S.A., on or about                , 2018.

Because our affiliate, Capital One Securities, Inc., is participating in the sale of the notes, the offering is being conducted in compliance with Financial Industry Regulatory Authority (“FINRA”) Rule 5121, as administered by FINRA.

Joint Book-Running Managers

The date of this prospectus supplement is                , 2018.

TABLE OF CONTENTS

You should rely only on the information contained in or incorporated by reference in this prospectus supplement and the accompanying prospectus. We have not, and the underwriters have not, authorized any other person to provide you with different information. If anyone provides you with different or inconsistent information, you should not rely on it. We are not, and the underwriters are not, making an offer to sell the notes in any jurisdiction where the offer or sale is not permitted. You should assume that the information appearing in this prospectus supplement (including any related free writing prospectus prepared by us or on our behalf, if any), the accompanying prospectus and the documents incorporated by reference herein and therein, is accurate only as of their respective dates. Our business, financial condition, results of operations and prospects may have changed since those dates.

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ABOUT THIS PROSPECTUS SUPPLEMENT

We provide information to you about the notes in two separate documents: (1) this prospectus supplement (including any related free writing prospectus prepared by us or on our behalf, if any), which describes the specific terms of the notes and also adds to and updates information contained in the accompanying prospectus and the documents incorporated by reference in that prospectus, and (2) the accompanying prospectus, which provides general information about securities we may offer from time to time, including securities other than the notes that are being offered by this prospectus supplement. If information in this prospectus supplement or any related free writing prospectus, if any, is inconsistent with the accompanying prospectus, you should rely on this prospectus supplement and such related free writing prospectus, if any.

It is important for you to read and consider all of the information contained in this prospectus supplement and any related free writing prospectus, if any, and the accompanying prospectus in making your investment decision. You also should read and consider the information in the documents we have referred you to in the section entitled “Where You Can Find More Information” beginning on page S-25 of this prospectus supplement and page 4 of the accompanying prospectus.

We include cross-references in this prospectus supplement and the accompanying prospectus to captions in these materials where you can find additional related discussions. The table of contents in this prospectus supplement provides the pages on which these captions are located.

Unless the context requires otherwise, references to “Capital One,” “issuer,” “we,” “our,” or “us” in this prospectus supplement refer to Capital One Financial Corporation, a Delaware corporation.

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FORWARD-LOOKING STATEMENTS

This prospectus supplement, the accompanying prospectus and the documents incorporated by reference herein and therein contain forward-looking statements. Statements that are not historical facts, including statements about our beliefs and expectations, are forward-looking statements within the meaning of Section 27A of the Securities Act of 1933, as amended (the “Securities Act”), and Section 21E of the Securities Exchange Act of 1934, as amended (the “Exchange Act”). Forward-looking statements include those that discuss, among other things, strategies, goals, outlook or other non-historical matters; projections, revenues, income, returns, expenses, capital measures, accruals for claims in litigation and for other claims against us; earnings per share or other financial measures for us; future financial and operating results; our plans, objectives, expectations and intentions; and the assumptions that underlie these matters. Forward-looking statements often use words such as “will,” “anticipate,” “target,” “expect,” “estimate,” “intend,” “plan,” “goal,” “believe” or other words of similar meaning. We have based these forward-looking statements on our current plans, estimates and projections, and you should not unduly rely on them. To the extent that any of the information in this prospectus supplement, the accompanying prospectus and the documents incorporated by reference herein and therein is forward-looking, it is intended to fit within the safe harbor for forward-looking information provided by the Private Securities Litigation Reform Act of 1995.

Numerous factors could cause our actual results to differ materially from those described in such forward-looking statements, including, among other things:

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You should carefully consider the factors referred to above in evaluating these forward-looking statements.

When considering these forward-looking statements, you should keep in mind these risks, uncertainties and other cautionary statements made in this prospectus supplement, the accompanying prospectus and in the documents incorporated by reference. See the factors set forth under the “Risk Factors” section beginning on page S-4 of this prospectus supplement and in any other documents incorporated or deemed to be incorporated by reference therein or herein, including our Annual Report on Form 10-K for the year ended December 31, 2017, as such discussion may be amended or updated in other reports filed by us with the SEC, for additional information that you should consider carefully in evaluating these forward-looking statements.

Forward-looking statements are not guarantees of future performance. They involve risks, uncertainties and assumptions, including the risk factors referred to above. Our future performance and actual results may differ materially from those expressed in forward-looking statements. Many of the factors that will determine these results and values are beyond our ability to control or predict. Any forward-looking statements made by us or on our behalf speak only as of the date they are made or as of the date indicated, and we do not undertake any obligation to update forward-looking statements as a result of new information, future events or otherwise.

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RISK FACTORS

Investing in the notes involves risks, including the risks described below that are specific to the notes and those that could affect us and our business. You should not purchase notes unless you understand these investment risks. Please be aware that other risks may prove to be important in the future. New risks may emerge at any time, and we cannot predict such risks or estimate the extent to which they may affect our financial performance. Before purchasing any notes, you should consider carefully the risks and other information in this prospectus supplement and the accompanying prospectus and carefully read the risks described in the documents incorporated by reference in this prospectus supplement and the accompanying prospectus, including the discussion under the “Risk Factors” section in our Annual Report on Form 10-K for the year ended December 31, 2017, as such discussion may be amended or updated in other reports filed by us with the SEC.

The notes are our obligations and not obligations of our subsidiaries and will be effectively subordinated to the claims of our subsidiaries’ creditors.

The notes are exclusively our obligations and not those of our subsidiaries. We are a holding company and, accordingly, substantially all of our operations are conducted through our subsidiaries. As a result, our cash flow and our ability to service our debt, including the notes, depend upon the earnings of our subsidiaries. In addition, we depend on the distribution of earnings, loans or other payments by our subsidiaries to us.

Our subsidiaries are separate and distinct legal entities. Our subsidiaries have no obligation to pay any amounts due on the notes or to provide us with funds to pay our obligations, whether by dividends, distributions, loans or other payments. In addition, any payment of dividends, distributions, loans or advances by our subsidiaries to us would be subject to regulatory or contractual restrictions. Payments to us by our subsidiaries also will be contingent upon those subsidiaries’ earnings and business considerations.

Our right to receive any assets of any of our subsidiaries upon their liquidation or reorganization, and, therefore, the right of the holders of the notes to participate in those assets, will be effectively subordinated to the claims of those subsidiaries’ creditors, including senior and subordinated debtholders and general trade creditors. In the event of any such distribution of assets of our bank subsidiaries, the claims of depositors and other general or subordinated creditors would be entitled to priority over the claims of holders of the notes. In addition, even if we were a creditor of any of our subsidiaries, our rights as a creditor would be subordinate to any security interest in the assets of those subsidiaries and any indebtedness of those subsidiaries senior to that held by us.

The notes will not be guaranteed by the FDIC or any other governmental agency.

The notes are not bank deposits and are not insured by the FDIC or any other governmental agency, nor are they obligations of, or guaranteed by, a bank. The notes will be obligations of Capital One Financial Corporation only and will not be guaranteed by any of our subsidiaries, including COBNA or CONA, our principal banking subsidiaries.

The indenture governing the notes does not contain any limitations on our ability to incur additional indebtedness, sell or otherwise dispose of assets, pay dividends or repurchase our capital stock.

Neither we nor any of our subsidiaries is restricted from incurring additional indebtedness or other liabilities, including additional senior indebtedness, under the indenture governing the terms of the notes. If we incur additional indebtedness or liabilities, our ability to pay our obligations on the notes could be adversely affected. We expect that we will from time to time incur additional indebtedness and other liabilities. In addition, we are not restricted under the indenture governing the notes from paying dividends or issuing or repurchasing our securities.

In addition, there are no financial covenants in the indenture. You are not protected under the indenture in the event of a highly leveraged transaction, reorganization, default under our existing indebtedness, restructuring,

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merger or similar transaction that may adversely affect you, except to the extent set forth under “Description of Debt Securities—Covenants” and “—Consolidation, Merger and Sale of Assets” in the accompanying prospectus would apply to the transaction.

Government regulation may affect the priority of the notes in the case of a bankruptcy or liquidation.

The Dodd-Frank Act created a new resolution regime known as the “orderly liquidation authority.” Under the orderly liquidation authority, the FDIC may be appointed as receiver for an entity, including a bank holding company, for purposes of liquidating the entity if the Secretary of the Treasury, following a process set out in the Dodd-Frank Act, determines that the entity is in default or danger of default and that the entity’s failure and its resolution under otherwise applicable law would have serious adverse effects on the financial stability of the United States.

If the FDIC is appointed as receiver under the orderly liquidation authority, then the Dodd-Frank Act, rather than applicable insolvency laws, would determine the powers of the receiver, and the rights and obligations of creditors and other parties who have dealt with the institution. There are substantial differences in the rights of creditors under the orderly liquidation authority compared to those under the U.S. Bankruptcy Code, including the power of the FDIC to disregard the strict priority of creditor claims in some circumstances, the use of an administrative claims procedure to determine creditors’ claims (as opposed to the judicial procedure utilized in bankruptcy proceedings) and the power of the FDIC to transfer claims to a “bridge” entity. As a consequence of the power of the FDIC under the orderly liquidation authority, the holders of the notes may be fully subordinated to interests held by the U.S. government and others in the event that we enter into a receivership, insolvency, liquidation or similar proceeding. Although the FDIC has issued regulations to implement the orderly liquidation authority, not all aspects of how the FDIC might exercise this authority are known and additional rulemakings are likely. Further, it is uncertain how the FDIC might exercise its discretion under the orderly liquidation authority in a particular case.

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USE OF PROCEEDS

We estimate that the net proceeds from this offering, after deducting the underwriting discounts and offering expenses payable by us, will be approximately $        . We intend to use the net proceeds from the sale of the notes for general corporate purposes in the ordinary course of our business. General corporate purposes may include repayment of debt, redemptions and repurchases of shares of our common stock and of our other securities, acquisitions, additions to working capital, capital expenditures and investments in our subsidiaries.

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DESCRIPTION OF THE NOTES

The following is a description of the particular terms of the notes offered pursuant to this prospectus supplement. This description supplements and, to the extent inconsistent, modifies the description of the general terms and provisions of senior debt securities set forth in the accompanying prospectus under “Description of Debt Securities.” To the extent the description in this prospectus supplement is inconsistent with the description contained in the accompanying prospectus, you should rely on the description in this prospectus supplement. The following description is qualified in its entirety by reference to the provisions of the senior indenture dated as of November 1, 1996, between us and The Bank of New York Mellon Trust Company, N.A., formerly known as The Bank of New York Trust Company, N.A. (as successor to Harris Trust and Savings Bank), as indenture trustee, which we refer to as the senior indenture. A copy of the senior indenture is filed as an exhibit to the registration statement of which this prospectus supplement and the accompanying prospectus are a part. Capitalized terms not defined in this section have the meanings assigned to such terms in the accompanying prospectus or in the senior indenture.

General

The 2021 fixed rate notes and the 2025 fixed rate notes offered hereby constitute separate series of senior debt securities described in the accompanying prospectus to be issued under the senior indenture. The notes will be our direct, unsecured obligations.

The 2021 fixed rate notes are initially offered in the principal amount of $            , and the 2025 fixed rate notes are initially offered in the principal amount of $        . We may, without the consent of existing holders, increase the principal amount of any series of notes by issuing more notes in the future, on the same terms and conditions (other than any differences in the issue date, the price to the public and the first interest payment date) and with the same CUSIP number (if appropriate), as the notes being offered by this prospectus supplement. We do not plan to inform existing holders if we reopen a series of notes to issue and sell additional notes in the future.

As used herein, the term “business day” means, any day that is not a Saturday or Sunday and that is not a day on which banking institutions in New York, New York, Chicago, Illinois or McLean, Virginia are generally authorized or obligated by law to close.

Payments

2021 Fixed Rate Notes

The 2021 fixed rate notes will mature on                 , 2021. The notes will bear interest from                 , 2018 at the annual rate of     %. We will pay interest on the notes semi-annually in arrears on each                 and                . We will make the first interest payment on                 , 2018.

2025 Fixed Rate Notes

The 2025 fixed rate notes will mature on                 , 2025. The notes will bear interest from                 , 2018 at the annual rate of     %. We will pay interest on the notes semi-annually in arrears on each                 and                 . We will make the first interest payment on                 , 2018.

General

We will pay interest to the person in whose name the note is registered at the close of business on the fifteenth calendar day (whether or not a business day) immediately preceding the relevant interest payment date, except that we will pay interest payable at the maturity date of the notes to the person or persons to whom principal is payable.

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Interest on the 2021 fixed rate notes and the 2025 fixed rate notes will be paid on the basis of a 360-day year comprised of twelve 30-day months. If any date on which interest is payable on the 2021 fixed rate notes or the 2025 fixed rate notes is not a business day, the payment of the interest payable on that date will be made on the next day that is a business day, without any interest or other payment in respect of the delay, with the same force and effect as if made on the scheduled payment date. If the maturity date of the 2021 fixed rate notes or the 2025 fixed rate notes falls on a day that is not a business day, the payment of interest and principal shall be made on the next succeeding business day, and no interest will accrue after such maturity date.

The notes offered hereby will not have the benefit of a sinking fund—that is, we will not deposit money on a regular basis into any separate custodial account to repay the notes.

Optional Redemption

The notes are not subject to repayment at the option of the holders at any time prior to maturity.

On or after                 , 2021 (which is the date that is one month prior to the maturity date of the 2021 fixed rate notes), the 2021 fixed rate notes will be redeemable upon not less than 10 nor more than 60 days’ prior notice given to the holders of the 2021 fixed rate notes to be redeemed, at a redemption price equal to 100% of the principal amount of the 2021 fixed rate notes to be redeemed plus accrued and unpaid interest to the date of redemption.

On or after                , 2025 (which is the date that is one month prior to the maturity date of the 2025 fixed rate notes), the 2025 fixed rate notes will be redeemable upon not less than 10 nor more than 60 days’ prior notice given to the holders of the 2025 fixed rate notes to be redeemed, at a redemption price equal to 100% of the principal amount of the 2025 fixed rate notes to be redeemed plus accrued and unpaid interest to the date of redemption.

If money sufficient to pay the redemption price of and accrued interest on any series of notes (or portions thereof) to be redeemed on the applicable redemption date is deposited with the Trustee or paying agent on or before the applicable redemption date and certain other conditions are satisfied, then on and after such redemption date, interest will cease to accrue on such series of notes (or such portion thereof) called for redemption and such series of notes will cease to be outstanding. If any redemption date is not a business day, we will pay the redemption price on the next business day without any interest or other payment due to the delay.

If fewer than all of a series of notes are to be redeemed, the depository will select the notes of such series for redemption on a pro rata basis, by lot or by such other method in accordance with the depository’s procedures. No notes of $2,000 or less will be redeemed in part.

Denominations

The notes will be issued in minimum denominations of $2,000 and in integral multiples of $1,000 in excess thereof.

Ranking

Payments of the principal and interest on the notes will rank equally with all of Capital One’s other unsecured and unsubordinated debt. Capital One’s senior indebtedness ranks pari passu with the notes. The notes will be our exclusive obligations and not those of our subsidiaries. Since we are a holding company and substantially all of our operations are conducted through subsidiaries, our cash flow and consequently our ability to service debt, including the notes, depend upon the earnings of our subsidiaries and the distribution of those earnings to us or upon other payments of funds by those subsidiaries to us. The subsidiaries are separate and distinct legal entities and have no obligation, contingent or otherwise, to pay any amounts due on the notes or to

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provide us with funds for payments on the notes, whether by dividends, distributions, loans or other payments. In addition, the payment of dividends and distributions and the making of loans and advances to us by our subsidiaries may be subject to regulatory, statutory or contractual restrictions, are contingent upon the earnings of those subsidiaries, and are subject to various business considerations.

Any right we have to receive assets of any of our subsidiaries upon their liquidation or reorganization and the resulting right of the holders of notes to participate in those assets effectively will be subordinated to the claims of that subsidiary’s creditors, including trade creditors, except to the extent that we are recognized as a creditor of the subsidiary, in which case our claims would be subordinated to any security interests in the assets of the subsidiary and any indebtedness of the subsidiary senior to the debt held by us.

The senior indenture does not limit the amount of additional senior indebtedness that we or any of our subsidiaries may incur. We may, without the consent of the holders of the notes, create and issue additional debt securities under the senior indenture ranking equally with the notes.

As of December 31, 2017, Capital One Financial Corporation had approximately $11.4 billion in senior unsecured indebtedness outstanding. As of December 31, 2017, our consolidated banking subsidiaries, CONA and COBNA, had approximately $12.1 billion and $4.3 billion in senior and subordinated indebtedness outstanding, respectively.

Events of Default

Events of default under the senior indenture with respect to the notes of a series are:

(1) failure to pay interest on the notes of such series when due and continuance of that default for 30 days;

(2) failure to pay the principal of the notes of such series when due and payable;

(3) failure to perform or the breach of any covenant or warranty in the senior indenture or the notes of such series (other than a covenant or warranty included solely for the benefit of a series of debt securities other than the notes of such series) that continues for 60 days after we are given written notice by the indenture trustee or we and the indenture trustee are given written notice by the holders of at least 25% in principal amount of the outstanding notes of such series;

(4) any event of default under any mortgage, indenture or other instrument securing or evidencing any indebtedness of us or any significant subsidiary for money borrowed, resulting in such indebtedness in principal amount exceeding $10,000,000 becoming or being declared due and payable prior to the date on which it would otherwise become due and payable, if the acceleration is not rescinded or annulled within 30 days after written notice; or

(5) certain events of bankruptcy, insolvency or reorganization of us or any of our significant subsidiaries.

Defeasance and Discharges

The defeasance provisions of the senior indenture described under “Description of Debt Securities—Legal Defeasance and Covenant Defeasance” in the accompanying prospectus will apply to the notes.

Same-Day Settlement and Payment

Settlement by purchasers of the notes will be made in immediately available funds. All payments by us to the depositary of principal and interest will be made in immediately available funds. So long as any notes are represented by global securities registered in the name of the depositary or its nominee, those notes will trade in

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the depositary’s Same-Day Funds Settlement System which requires secondary market trading in those notes to settle in immediately available funds. No assurance can be given as to the effect, if any, of this requirement to settle in immediately available funds on trading activity in notes.

Global Securities; Book-Entry Issue

We expect that the notes will be issued in the form of global securities held by The Depository Trust Company and its participants, including Euroclear System and Clearstream Banking, S.A., as described under “Book-Entry Procedures and Settlement” in the accompanying prospectus.

Trustee

The Bank of New York Mellon Trust Company, N.A., formerly known as The Bank of New York Trust Company, N.A. (as successor to Harris Trust and Savings Bank) is the indenture trustee with respect to the notes. The indenture trustee is one of a number of banks with which we and our subsidiaries maintain banking and trust relationships in the ordinary course of business.

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MATERIAL UNITED STATES FEDERAL INCOME TAX CONSEQUENCES

This section summarizes the material U.S. federal income tax considerations relating to the purchase, ownership, and disposition of the notes. This summary does not provide a complete analysis of all potential tax considerations. The information provided below is based on the Internal Revenue Code of 1986, as amended (referred to herein as the “Code”), Treasury regulations issued under the Code, judicial authority and administrative rulings and practice, all as of the date of this prospectus supplement and all of which are subject to change, possibly on a retroactive basis. As a result, the tax considerations of purchasing, owning or disposing of the notes could differ from those described below. This summary deals only with beneficial owners who purchase the notes on original issuance at the first price at which a substantial portion of the notes is sold for cash (other than to bond houses, brokers or similar persons or organizations acting in the capacity of underwriters, placement agents or wholesalers) and who hold the notes as “capital assets” within the meaning of Section 1221 of the Code. This summary does not deal with persons in special tax situations, such as financial institutions, insurance companies, S corporations, regulated investment companies, real estate investment trusts, tax exempt investors, dealers in securities and currencies, traders in securities that elect to use a mark-to-market method of accounting for their securities, controlled foreign corporations, corporations that accumulate earnings to avoid U.S. federal income tax, U.S. expatriates, persons holding notes as a position in a “straddle,” “hedge,” “conversion transaction,” or other integrated transaction for U.S. federal income tax purposes, persons subject to special tax accounting rules under Section 451(b) of the Code, investors in pass-through entities, or U.S. holders (as defined below) whose functional currency is not the U.S. dollar. Further, this discussion does not address the consequences under U.S. alternative minimum tax rules, U.S. federal estate or gift tax laws, the tax laws of any U.S. state or locality, any non-U.S. tax laws, or any tax laws other than income tax laws. We will not seek a ruling from the Internal Revenue Service (the “IRS”) with respect to any of the matters discussed herein and there can be no assurance that the IRS will not challenge one or more of the tax consequences described herein.

As used herein, the term “U.S. Person” means:

As used herein, a “U.S. holder” is a beneficial owner of notes that is, for U.S. federal income tax purposes, a U.S. Person. As used herein, the term “non-U.S. holder” means a beneficial owner, other than a partnership (or entity treated as a partnership for U.S. federal income tax purposes), of notes that is not a U.S. holder.

If a partnership, including for this purpose any entity treated as a partnership for U.S. federal income tax purposes, is a beneficial owner of notes, the treatment of a partner in the partnership generally will depend upon the status of the partner and upon the activities of the partnership. A holder of notes that is a partnership and partners in such a partnership should consult their independent tax advisors about the U.S. federal income tax consequences of holding and disposing of notes.

Investors should consult their tax advisor concerning the tax consequences of the ownership and disposition of the notes, including the tax consequences under the laws of any foreign, state, local or other taxing jurisdictions and the possible effects on investors of changes in U.S. federal or other tax laws.

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U.S. holders

Interest

It is anticipated, and this discussion assumes, that the notes will be issued without original issue discount for U.S. federal income tax purposes. In such case, interest on a note will be includable by a U.S. holder as interest income at the time it accrues or is received in accordance with such holder’s method of accounting for U.S. federal income tax purposes and will be ordinary income.

Sale, Exchange, Redemption, Retirement or Other Taxable Disposition of the Notes

Upon a sale, exchange, redemption, retirement or other taxable disposition of a note, a U.S. holder will generally recognize gain or loss equal to the difference between (i) the amount realized on the disposition (other than amounts attributable to accrued but unpaid interest, which will be taxed as interest income as discussed above to the extent not previously included in income) and (ii) the U.S. holder’s tax basis in the note. A U.S. holder’s tax basis in a note generally will equal the cost of the note. A U.S. holder’s gain or loss will generally constitute capital gain or loss and will be long-term capital gain or loss if the U.S. holder has held such note for longer than one year. The deductibility of capital losses is subject to certain limitations. Net long-term capital gain recognized by a non-corporate U.S. holder is generally taxed at preferential rates.

Medicare Tax

U.S. holders who are individuals, estates or certain trusts are required to pay an additional 3.8% Medicare tax on the lesser of (1) the U.S. person’s “net investment income” for the relevant taxable year and (2) the excess of the U.S. person’s modified gross income for the taxable year over a certain threshold (which in the case of individuals will be between $125,000 and $250,000 depending on the individual’s circumstances). Net investment income will generally include interest income and net gains from the disposition of the notes, unless such interest income or net gains are derived in the ordinary course of the conduct of a trade or business (other than a trade or business that consists of certain passive or trading activities). A U.S. holder that is an individual, estate or trust should consult its tax advisor regarding the applicability of the Medicare tax to its income and gains in respect of its investment in the notes.

Backup Withholding and Information Reporting

In general, a U.S. holder of a note will be subject to backup withholding at the applicable tax rate with respect to payments of interest or the gross proceeds from dispositions of notes, unless the holder (i) is an entity that is exempt from backup withholding (generally including tax-exempt organizations and certain qualified nominees) and, when required, provides appropriate documentation to that effect, (ii) provides us or our paying agent with the holder’s social security number or other taxpayer identification number (“TIN”), certifies that the TIN provided is correct and that the holder has not been notified by the IRS that it is subject to backup withholding due to underreporting of interest or dividends, and otherwise complies with applicable requirements of the backup withholding rules. In addition, such payments to U.S. holders that are not exempt entities will generally be subject to information reporting requirements. A U.S. holder who does not provide us or our paying agent with the correct TIN may be subject to penalties imposed by the IRS. The amount of any backup withholding from a payment to a U.S. holder will be allowed as a credit against such holder’s U.S. federal income tax liability and may entitle such holder to a refund, provided that the required information is timely furnished to the IRS.

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Non-U.S. holders

Interest

Subject to the discussions of backup withholding and the Foreign Account Tax Compliance Act (“FATCA”) below, interest income of a non-U.S. holder will qualify for the “portfolio interest exemption” and therefore not be subject to U.S. federal income tax or withholding, provided that:

If any of these conditions are not met, interest on the notes paid to a non-U.S. holder will generally be subject to U.S. federal income tax and withholding at a 30% rate unless (a) an applicable income tax treaty reduces or eliminates such tax, and the non-U.S. holder claims the benefit of that treaty by providing an IRS Form W-8BEN or IRS Form W-8BEN-E (or a suitable substitute or successor form or such other form as the IRS may prescribe) that has been properly completed and duly executed, or (b) the interest is ECI and the non-U.S. holder complies with applicable certification requirements by providing an IRS Form W-8ECI (or a suitable substitute or successor form or such other form as the IRS may prescribe) that has been properly completed and duly executed.

If the interest on the notes is ECI, the non-U.S. holder will be required to pay U.S. federal income tax on that interest on a net income basis generally in the same manner as a U.S. holder (and the 30% withholding tax described above will not apply, provided the appropriate statement is provided to us or our paying agent). If a non-U.S. holder is eligible for the benefits of any income tax treaty between the United States and its country of residence, any interest income that is ECI will be subject to U.S. federal income tax in the manner specified by the treaty and will generally be subject to U.S. federal income tax only if such income is attributable to a permanent establishment or a fixed base maintained by the non-U.S. holder in the United States and the non-U.S. holder claims the benefit of the treaty by providing a Form W-8BEN or a Form W-8BEN-E (or a suitable substitute or successor form or such other form as the IRS may prescribe) that has been properly completed and duly executed. In addition, interest received by a corporate non-U.S. holder that is ECI may also, under certain circumstances, be subject to an additional “branch profits tax” at a 30% rate, or, if applicable, a lower treaty rate.

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Sale, Exchange, Redemption, Retirement or Other Taxable Disposition of the Notes

Subject to the discussion of backup withholding and FATCA below, a non-U.S. holder will generally not be subject to U.S. federal income tax on any gain realized on a sale, exchange, redemption, retirement or other taxable disposition of the notes unless:

If a non-U.S. holder falls under the first of these exceptions, the holder will be taxed on the net gain derived from the disposition under the graduated U.S. federal income tax rates that are applicable to U.S. Persons and, if the non-U.S. holder is a foreign corporation, it may also be subject to the branch profits tax described above. Even though the ECI will be subject to U.S. federal income tax, and possibly subject to the branch profits tax, it will not be subject to withholding if the non-U.S. holder delivers an appropriate IRS Form W-8ECI (or a suitable substitute or successor form or such other form as the IRS may prescribe) that has been properly completed and duly executed to us or our agent.

If an individual non-U.S. holder falls under the second of these exceptions, the holder generally will be subject to U.S. federal income tax at a rate of 30% on the amount by which the gain derived from the disposition exceeds such holder’s capital losses allocable to sources within the United States for the taxable year of the sale.

Backup Withholding and Information Reporting

Generally, the amount of interest paid to you and the amount of tax, if any, withheld with respect to those payments must be reported annually to the IRS and to you. Copies of the information returns reporting such interest, and withholding may also be made available to the tax authorities in the country in which you reside under the provisions of an applicable income tax treaty. Backup withholding will generally not apply to payments of interest on the notes by us or our paying agent if a holder certifies its status as a non-U.S. holder under penalties of perjury or otherwise establishes an exemption (provided that neither we nor our paying agent has actual knowledge that it is a U.S. Person or that the conditions of any other exemptions are not in fact satisfied).

The payment of the proceeds of the disposition of notes to or through the United States office of a United States or foreign broker will be subject to information reporting and, depending on the circumstances, backup withholding unless the non-U.S. holder provides the certification described above or otherwise establishes an exemption (and neither we nor our paying agent has actual knowledge that the holder is a U.S. Person or that the conditions of any other exemptions are not in fact satisfied). The proceeds of a disposition effected outside the United States by a holder of the notes to or through a foreign office of a broker generally will not be subject to backup withholding or information reporting. However, if that broker is, for United States federal income tax purposes, a U.S. Person, a controlled foreign corporation, a foreign person 50% or more of whose gross income from all sources for certain periods is effectively connected with a trade or business in the United States, or a foreign partnership that is engaged in the conduct of a trade or business in the United States or that has one or more partners that are U.S. Persons who in the aggregate hold more than 50% of the income or capital interests in the partnership, information reporting requirements will apply unless that broker has documentary evidence in its files of such holder’s status as a non-U.S. holder and has no actual knowledge to the contrary or unless such holder otherwise establishes an exemption.

Any amounts withheld from a payment to a holder under the backup withholding rules will be allowed as a credit against such holder’s U.S. federal income tax liability and may entitle it to a refund, provided it timely furnishes the required information to the IRS.

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FATCA

Under FATCA, a 30% withholding tax may be imposed on interest (including original issue discount) on notes issued to a foreign financial institution (including amounts paid to a foreign financial institution on or behalf of a holder) and certain other non-financial foreign entities. Additionally, after December 31, 2018, a 30% withholding may apply to gross proceeds from the disposition of such notes.

Withholding under FATCA generally will not apply where such payments are made to (1) a foreign financial institution that undertakes, under either an agreement with the U.S. Treasury or pursuant to an intergovernmental agreement between the jurisdiction in which it is a resident and the U.S. Treasury, to generally identify accounts held by certain U.S. persons and foreign entities with substantial U.S. owners, annually report certain information about such accounts and withhold 30% on payments made to non-compliant foreign financial institutions and certain other account holders, (2) a non-financial foreign entity that either certifies it does not have any substantial U.S. owners or furnishes identifying information regarding each substantial U.S. owner, or (3) a foreign financial institution or a non-financial foreign entity that otherwise qualifies for an exemption from these rules.

Investors should consult their tax advisors regarding FATCA and the regulations thereunder.

The U.S. federal tax discussion set forth above as to both U.S. holders and non-U.S. holders is included for general information only and may not be applicable depending upon a holder’s particular situation. Holders should consult their tax advisors with respect to the tax consequences to them of the ownership and disposition of the notes, including the tax consequences under state, local, foreign and other tax laws and the possible effects of changes in U.S. federal or other tax laws.

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CERTAIN ERISA CONSIDERATIONS

The following is a summary of certain considerations associated with the purchase of the notes by employee benefit plans to which Title I of the U.S. Employee Retirement Income Security Act of 1974, as amended (“ERISA”), applies; plans, individual retirement accounts and other arrangements to which Section 4975 of the Code applies and plans or arrangements to which the provisions of any federal, state, local, non-U.S. or other laws or regulations that are similar to such provisions of ERISA or the Code (“Similar Laws”), apply; and entities whose underlying assets are considered to include “plan assets” of such plans, accounts and arrangements (each of which is referred to hereunder as a “Plan”).

Each fiduciary of a Plan should consider the fiduciary standards of ERISA or any applicable Similar Laws in the context of the Plan’s particular circumstances before authorizing an investment in the notes. Accordingly, among other factors, the fiduciary should consider whether the investment would satisfy the prudence and diversification requirements of ERISA or any applicable Similar Laws and would be consistent with the documents and instruments governing the Plan.

Section 406 of ERISA and Section 4975 of the Code prohibit Plans subject to such provisions (“ERISA Plans”) from engaging in certain transactions involving “plan assets” with persons that are “parties in interest” under ERISA or “disqualified persons” under the Code with respect to the ERISA Plans. A violation of these “prohibited transaction” rules may result in an excise tax or other liabilities under ERISA and/or Section 4975 of the Code for those persons, unless exemptive relief is available under an applicable statutory or administrative exemption. Employee benefit plans that are governmental plans (as defined in Section 3(32) of ERISA), certain church plans (as defined in Section 3(33) of ERISA) and foreign plans (as described in Section 4(b)(4) of ERISA) are not subject to the requirements of ERISA or Section 4975 of the Code, but may be subject to Similar Laws (such Plans referred to herein as “Similar Law Plans”).

Prohibited transactions within the meaning of Section 406 of ERISA or Section 4975 of the Code could arise if the notes were acquired by an ERISA Plan with respect to which we or any of our affiliates are a party in interest or a disqualified person. For example, if we are a party in interest or disqualified person with respect to an investing ERISA Plan (either directly or by reason of our ownership of our subsidiaries), an extension of credit prohibited by Section 406(a)(1)(B) of ERISA and Section 4975(c)(1)(B) of the Code between the investing ERISA Plan and us may be deemed to occur, unless exemptive relief were available under an applicable exemption (see below).

Prohibited transaction class exemptions, or PTCEs, issued by the United States Department of Labor, as well as certain statutory exemptions available under ERISA and the Code, may provide exemptive relief for direct or indirect prohibited transactions resulting from the purchase, holding or disposition of the notes. Those class and statutory exemptions include:

Because of the possibility that direct or indirect prohibited transactions or violations of Similar Laws could occur as a result of the purchase, holding or disposition of the notes by a Plan, the notes may not be purchased by

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any Plan, or any person investing the assets of any Plan, unless its purchase, holding and disposition of the notes will not constitute or result in a non-exempt prohibited transaction under ERISA or the Code or in a violation of any Similar Laws. Any purchaser or holder of the notes or any interest in the notes will be deemed to have represented in its fiduciary and its corporate capacity by its purchase and holding of the notes that either:

In addition, any person purchasing notes on behalf of an ERISA Plan (the “Plan Fiduciary”) will be deemed to have represented, in its corporate and its fiduciary capacity, by its purchase and holding of the notes (the “Transaction”) that:

(1) neither we, the indenture trustee nor the underwriters, nor any of their affiliates (each, referred to herein as a “Transaction Party”) has provided or will provide impartial investment advice or give advice in a fiduciary capacity with respect to the acquisition of the notes by the ERISA Plan, other than to the Plan Fiduciary which is independent of the Transaction Parties, and the Plan Fiduciary either:

(a) is a bank as defined in Section 202 of the Investment Advisers Act of 1940 (the “Advisers Act”), or similar institution that is regulated and supervised and subject to periodic examination by a State or Federal agency;

(b) is an insurance carrier that is qualified under the laws of more than one state to perform the services of managing, acquiring or disposing of assets of an ERISA Plan;

(c) is an investment adviser registered under the Advisers Act, or, if not registered as an investment adviser under the Advisers Act by reason of paragraph (1) of Section 203A of the Advisers Act, is registered as an investment adviser under the laws of the state in which it maintains its principal office and place of business;

(d) is a broker-dealer registered under the Exchange Act; or

(e) has, and at all times that the ERISA Plan is invested in the notes will have, total assets of at least U.S. $50,000,000 under its management or control (provided that this clause (e) shall not be satisfied if the Plan Fiduciary is either (i) the owner or a relative of the owner of an investing IRA or (ii) a participant or beneficiary of the ERISA Plan investing in the notes in such capacity);

(2) the Plan Fiduciary is capable of evaluating investment risks independently, both in general and with respect to particular transactions and investment strategies, including the acquisition by the ERISA Plan of the notes;

(3) the Plan Fiduciary is a “fiduciary” with respect to the ERISA Plan within the meaning of Section 3(21) of ERISA, Section 4975 of the Code, or both, and is responsible for exercising independent judgment in evaluating the Plan’s acquisition of the notes;

(4) none of the Transaction Parties has exercised any authority to cause the ERISA Plan to invest in the notes or to negotiate the terms of the ERISA Plan’s investment in the notes; and

(5) the Plan Fiduciary acknowledges, and the Transaction Parties hereby notify the Plan Fiduciary:

(a) that none of the Transaction Parties is undertaking to provide impartial investment advice or to give advice in a fiduciary capacity, and that no such entity has given investment advice or otherwise made a recommendation, in connection with the ERISA Plan’s acquisition of the notes; and

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(b) of the existence and nature of the Transaction Parties’ financial interests in the ERISA Plan’s acquisition of the notes.

In addition, any purchaser that is a Similar Law Plan, including any fiduciary purchasing on behalf of a Similar Law Plan, will be deemed to have represented, in its corporate and its fiduciary capacity, by its acquisition and holding of the notes that (a) none of the Transaction Parties is a “fiduciary” with respect to the acquisition, holding or disposition of the notes, or as a result of any exercise by a Transaction Party of any rights in connection with the notes, (b) no advice provided by a Transaction Party has formed a primary basis for any investment decision by or on behalf of such purchaser in connection with the notes and the transactions contemplated with respect to the notes, and (c) such purchaser recognizes and agrees that any communication from the Transaction Parties to the purchaser with respect to the notes is not intended by the Transaction Parties to be impartial investment advice and is rendered in its capacity as a seller of such notes and not a fiduciary to such purchaser.

Due to the complexity of these rules and the penalties imposed upon persons involved in non-exempt prohibited transactions, it is important that any person considering the purchase of notes on behalf of or with the assets of any Plan consult with its counsel regarding the consequences under ERISA, the Code and any applicable Similar Laws of the acquisition, ownership and disposition of notes, whether any exemption would be applicable, and whether all conditions of such exemption have been satisfied such that the acquisition, holding and disposition of the notes by the Plan are entitled to full exemptive relief thereunder.

Nothing herein shall be construed as, and the sale of notes to a Plan is in no respect, a representation by us or the underwriters that any investment in the notes would meet any or all of the relevant legal requirements with respect to investment by, or is appropriate for, Plans generally or any particular Plan.

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UNDERWRITING

Under the terms and subject to the conditions contained in an underwriting agreement, dated                , 2018, we have agreed to sell to the underwriters named below, for whom Merrill Lynch, Pierce, Fenner & Smith Incorporated, J.P. Morgan Securities LLC, Morgan Stanley & Co. LLC, RBC Capital Markets, LLC and Capital One Securities, Inc. are acting as representatives, and the underwriters have severally agreed to purchase the respective principal amounts of the notes set forth opposite their names below:

The underwriting agreement provides that the obligations of the several underwriters to pay for and accept delivery of the notes are subject to, among other things, the approval of certain legal matters by their counsel and certain other conditions. The underwriters are obligated to purchase all of the notes offered by us if they purchase any of the notes. The underwriting agreement also provides that if an underwriter defaults, the purchase commitments of non-defaulting underwriters may be increased or the offering may be terminated. The offering of the notes by the underwriters is subject to receipt and acceptance and subject to the underwriters’ right to reject any order in whole or in part.

The underwriters initially propose to offer the notes directly to the public at the public offering price that appears on the cover page of this prospectus supplement and to certain dealers at that price less a selling concession not in excess of     % of the principal amount per 2021 fixed rate note, and not in excess of     % of the principal amount per 2025 fixed rate note. Any underwriter may allow, and such dealers may reallow, a selling concession not in excess of     % of the principal amount per 2021 fixed rate note, and not in excess of     % per 2025 fixed rate note, to certain other brokers or dealers. After the initial offering of the notes to the public, the underwriters may vary the offering price and other selling terms of the notes from time to time. Sales of notes made outside of the United States may be made by affiliates of the underwriters.

We estimate that our total expenses for this offering, excluding the underwriting discounts, will be approximately $         million.

We have agreed to indemnify the several underwriters against, or contribute to payments that the underwriters may be required to make in respect of, certain liabilities, including liabilities under the Securities Act.

In connection with this offering, the underwriters may engage in over-allotment, stabilizing transactions, syndicate covering transactions and penalty bids in accordance with Regulation M under the Exchange Act. Over-allotment involves sales in excess of the offering size, which create a short position for the underwriters. Stabilizing transactions involve bids to purchase the notes in the open market for the purpose of pegging, fixing or maintaining the price of the notes. Syndicate covering transactions involve purchases of the notes in the open market after the distribution has been completed in order to cover syndicate short positions. The underwriters may also impose a penalty bid. This occurs when a particular underwriter repays to the underwriters a portion of the underwriting discounts received by it because the representatives have repurchased notes sold by or for the account of such underwriter in stabilizing or short covering transactions.

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Any of these activities may have the effect of preventing or retarding a decline on the market price of the notes. They may also cause the price of the notes to be higher than the price that would otherwise exist in the open market in the absence of these transactions. If the underwriters engage in any of these transactions, they may discontinue any of them at any time, without notice. Neither we nor the underwriters make any representation or prediction as to the direction or magnitude of any effect that the transactions described above may have on the price of the notes.

The notes are a new issue of securities with no established trading market. The notes will not be listed on any securities exchange or on any automated dealer quotation system. The underwriters may make a market in the notes after completion of the offering, but will not be obligated to do so and may discontinue any market-making activities at any time without notice. No assurance can be given as to the liquidity of the trading market for the notes or that an active public market for such notes will develop. If an active public market for such notes does not develop, the market price and liquidity of such notes may be adversely affected.

The underwriters and their respective affiliates are full service financial institutions engaged in various activities, which may include securities trading, commercial and investment banking, financial advisory, investment management, investment research, principal investment, hedging, financing and brokerage activities. Certain of the underwriters and their respective affiliates have, from time to time, performed, and may in the future perform, various financial advisory and investment banking services for the issuer, for which they may receive customary fees and expenses.

One of the underwriters, Capital One Securities, Inc., is our affiliate. The distribution arrangements for this offering comply with the requirements of FINRA Rule 5121 regarding a FINRA member firm’s participation in the distribution of securities of an affiliate. In accordance with Rule 5121, no FINRA member firm that has a conflict of interest under Rule 5121 may make sales in this offering to any discretionary account without the prior approval of the customer. Capital One Securities, Inc. may use this prospectus supplement and the accompanying prospectus in connection with offers and sales of the notes in the secondary market. Capital One Securities, Inc. may act as principal or agent in those transactions. Secondary market sales will be made at prices related to market prices at the time of sale. Capital One Securities, Inc. is not primarily responsible for managing this offering.

In addition, in the ordinary course of their various business activities, the underwriters and their respective affiliates have made or held, and may in the future make or hold, a broad array of investments, including serving as counterparties to certain derivative and hedging arrangements, and may have actively traded, and, in the future may actively trade, debt and equity securities (or related derivative securities), and financial instruments (including bank loans) for their own account and for the accounts of their customers and may have in the past and at any time in the future hold long and short positions in such securities and instruments. Such investment and securities activities may have involved, and in the future may involve, securities and instruments of Capital One. If any of the underwriters or their affiliates have a lending relationship with us, certain of those underwriters or their affiliates routinely hedge, and certain other of those underwriters or their affiliates may hedge, their credit exposure to us consistent with their customary risk management policies. Typically, these underwriters and their affiliates would hedge such exposure by entering into transactions which consist of either the purchase of credit default swaps or the creation of short positions in our securities, including potentially the notes offered hereby. Any such credit default swaps or short positions could adversely affect future trading prices of the notes offered hereby. The underwriters and their affiliates may also make investment recommendations and/or publish or express independent research views in respect of such securities or financial instruments and may hold, or recommend to clients that they acquire, long and/or short positions in such securities and instruments.

Selling Restrictions

Canada

The notes may be sold only to purchasers purchasing, or deemed to be purchasing, as principal that are accredited investors, as defined in National Instrument 45-106 Prospectus Exemptions or subsection 73.3(1) of

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the Securities Act (Ontario), and are permitted clients, as defined in National Instrument 31-103 Registration Requirements, Exemptions and Ongoing Registrant Obligations. Any resale of the notes must be made in accordance with an exemption from, or in a transaction not subject to, the prospectus requirements of applicable securities laws.

Securities legislation in certain provinces or territories of Canada may provide a purchaser with remedies for rescission or damages if this prospectus supplement and the accompanying prospectus (including any amendment thereto) contains a misrepresentation, provided that the remedies for rescission or damages are exercised by the purchaser within the time limit prescribed by the securities legislation of the purchaser’s province or territory. The purchaser should refer to any applicable provisions of the securities legislation of the purchaser’s province or territory for particulars of these rights or consult with a legal advisor.

Pursuant to section 3A.3 of National Instrument 33-105 Underwriting Conflicts (“NI 33-105”), the underwriters are not required to comply with the disclosure requirements of NI 33-105 regarding underwriter conflicts of interest in connection with this offering.

European Economic Area—Prohibition of Sales to Retail Investors

The notes are not intended to be offered, sold or otherwise made available to and should not be offered, sold or otherwise made available to any retail investor in the European Economic Area (“EEA”). For these purposes, a “retail investor” means a person who is one (or more) of: (i) a retail client as defined in point (11) of Article 4(1) of Directive 2014/65/EU (as amended, “MiFID II”); or (ii) a customer within the meaning of Directive 2002/92/EC (as amended, the “Insurance Mediation Directive”), where that customer would not qualify as a professional client as defined in point (10) of Article 4(1) of MiFID II; or (iii) not a qualified investor as defined in the Prospectus Directive (as defined below). No key information document required by Regulation (EU) No 1286/2014 (as amended, the “PRIIPs Regulation”) for offering or selling packaged retail and insurance-based investment products or otherwise making them available to retail investors in the EEA has been prepared and therefore offering or selling the notes or otherwise making them available to any retail investor in the EEA may be unlawful under the PRIIPs Regulation.

This prospectus supplement has been prepared on the basis that any offer of notes in any Member State of the EEA which has implemented the Prospectus Directive (each, a “Relevant Member State”) will be made pursuant to an exemption under the Prospectus Directive from the requirement to publish a prospectus.

Accordingly any person making or intending to make an offer to the public (or otherwise) in a Relevant Member State of notes which are the subject of the offering contemplated in this prospectus supplement may only do so in circumstances in which no obligation arises for us or any of the underwriters to publish a prospectus pursuant to Article 3 of the Prospectus Directive in relation to such offer. Neither we nor the underwriters have authorized, nor do we or they authorize, the making of any offer of notes in circumstances in which an obligation arises for us or the underwriters to publish a prospectus for such offer. This prospectus supplement is not a prospectus or a supplementary prospectus for the purposes of the Prospectus Directive.

For the purpose of the above provisions, the expression “an offer of notes to the public” in relation to any notes in any Relevant Member State means the communication in any form and by any means of sufficient information on the terms of the offer and the notes to be offered so as to enable an investor to decide to purchase or subscribe for the notes, as the same may be varied in the Relevant Member State by any measure implementing the Prospectus Directive in the Relevant Member State and the expression “Prospectus Directive” means Directive 2003/71/EC (as amended, including by Directive 2010/73/EU) and includes any relevant implementing measure in the Relevant Member State.

Hong Kong

The notes may not be offered or sold in Hong Kong, by means of any document, other than (a) to “professional investors” as defined in the Securities and Futures Ordinance (Cap. 571, Laws of Hong Kong) and

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any rules made under that Ordinance or (b) in other circumstances which do not result in the document being a “prospectus” as defined in the Companies Ordinance (Cap. 32, Laws of Hong Kong) or which do not constitute an offer to the public within the meaning of that Ordinance. No advertisement, invitation or document relating to the notes may be issued or may be in the possession of any person for the purpose of the issue, whether in Hong Kong or elsewhere, which is directed at, or the contents of which are likely to be read by, the public in Hong Kong (except if permitted to do so under the laws of Hong Kong) other than with respect to the notes which are intended to be disposed of only to persons outside Hong Kong or only to “professional investors” as defined in the Securities and Futures Ordinance (Cap. 571, Laws of Hong Kong) or any rules made under that Ordinance.

Japan

No securities registration statement has been filed under Article 4, Paragraph 1 of the Financial Instruments and Exchange Law of Japan (Law No. 25 of 1948, as amended) (“FIEL”) in relation to the notes. The notes are being offered in a private placement to “qualified institutional investors” (tekikaku-kikan-toshika) under Article 10 of the Cabinet Office Ordinance concerning Definitions provided in Article 2 of the FIEL (the Ministry of Finance Ordinance No. 14, as amended) (“QIIs”), under Article 2, Paragraph 3, Item 2 i of the FIEL. Any QII acquiring the notes in this offer may not transfer or resell those notes except to other QIIs.

Korea

The notes may not be offered, sold and delivered directly or indirectly, or offered or sold to any person for reoffering or resale, directly or indirectly, in Korea or to any resident of Korea except pursuant to the applicable laws and regulations of Korea, including the Korea Securities and Exchange Act and the Foreign Exchange Transaction Law and the decrees and regulations thereunder. The notes have not been registered with the Financial Services Commission of Korea for public offering in Korea. Furthermore, the notes may not be resold to Korean residents unless the purchaser of the notes complies with all applicable regulatory requirements (including but not limited to government approval requirements under the Foreign Exchange Transaction Law and its subordinate decrees and regulations) in connection with the purchase of the notes.

Singapore

This prospectus supplement has not been registered as a prospectus with the Monetary Authority of Singapore. Accordingly, this prospectus supplement and any other document or material in connection with the offer or sale, or invitation for subscription or purchase, of the notes may not be circulated or distributed, nor may the notes be offered or sold, or be made the subject of an invitation for subscription or purchase, whether directly or indirectly, to persons in Singapore other than (i) to an institutional investor under Section 274 of the Securities and Future Act, Chapter 289 of Singapore (the “SFA”), (ii) to a “relevant person” as defined in Section 275(2) of the SFA, or any person pursuant to Section 275(1A), and in accordance with the conditions, specified in Section 275 of the SFA or (iii) otherwise pursuant to, and in accordance with the conditions of, any other applicable provision of the SFA.

Where the notes are subscribed and purchased under Section 275 of the SFA by a relevant person which is:

(a) a corporation (which is not an accredited investor (as defined in Section 4A of the SFA)) the sole business of which is to hold investments and the entire share capital of which is owned by one or more individuals, each of whom is an accredited investor; or

(b) a trust (where the trustee is not an accredited investor (as defined in Section 4A of the SFA)) whose sole whole purpose is to hold investments and each beneficiary is an accredited investor, shares, debentures and units of shares and debentures of that corporation or the beneficiaries’ rights and interest (howsoever described) in that

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trust shall not be transferable within six months after that corporation or that trust has acquired the notes under Section 275 of the SFA except:

(i) to an institutional investor under Section 274 of the SFA or to a relevant person (as defined in Section 275(2) of the SFA) and in accordance with the conditions, specified in Section 275 of the SFA;

(ii) (in the case of a corporation) where the transfer arises from an offer referred to in Section 275(1A) of the SFA, or (in the case of a trust) where the transfer arises from an offer that is made on terms that such rights or interests are acquired at a consideration of not less than S$200,000 (or its equivalent in a foreign currency) for each transaction, whether such amount is to be paid for in cash or by exchange of securities or other assets;

(iii) where no consideration is or will be given for the transfer; or

(iv) where the transfer is by operation of law.

By accepting this prospectus supplement, the recipient hereof represents and warrants that he is entitled to receive it in accordance with the restrictions set forth above and agrees to be bound by limitations contained herein. Any failure to comply with these limitations may constitute a violation of law.

Switzerland

The notes may not be offered, sold or advertised directly or indirectly into or in Switzerland except in a manner which will not result in a public offering within the meaning of article 652a or 1156 of the Swiss Federal Code of Obligations (“CO”) or a listing prospectus within the meaning of Article 27 et seq. of the Listing Rules of SIX Swiss Exchange. Neither this prospectus supplement and the accompanying prospectus nor any other offering or marketing materials relating to the notes have been prepared with regard to the disclosure standards for prospectuses under article 652a or 1156 CO, and therefore do not constitute a prospectus within the meaning of article 652a or 1156 CO.

Neither this prospectus supplement and the accompanying prospectus nor any other offering or marketing materials relating to the notes may be distributed, published or otherwise made available in Switzerland except in a manner which will not constitute a public offering of the notes into or in Switzerland.

Taiwan

The notes have not been and will not be registered with the Financial Supervisory Commission of Taiwan pursuant to relevant securities laws and regulations and may not be sold, issued or offered within Taiwan through a public offering or in circumstances which constitute an offer within the meaning of the Securities and

Exchange Act of Taiwan that requires a registration or approval of the Financial Supervisory Commission of Taiwan. No person or entity in Taiwan has been authorized to offer, sell, give advice regarding or otherwise intermediate the offering and sale of the notes in Taiwan.

United Kingdom

In the United Kingdom, this prospectus supplement is being distributed only to, and is directed only at, and any offer subsequently made may only be directed at persons who are non-retail investors who are also (i) persons having professional experience in matters relating to investments who fall within the definition of “investment professionals” in Article 19(5) of the Financial Services and Markets Act 2000 (Financial Promotion) Order 2005, as amended (the “Order”) and/or (ii) high net worth bodies corporate, unincorporated associations and partnerships and trustees of high value trusts as described in Article 49(2) of the Order (all such persons together being referred to as “relevant persons”). This document must not be acted on or relied on in the

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United Kingdom by persons who are not relevant persons. In the United Kingdom, any investment or investment activity to which this document relates is only available to, and will be engaged in with, relevant persons. For these purposes, non-retail investors means persons who are not retail investors as defined above under the heading “European Economic Area—Prohibition of Sales to Retail Investors”.

Each underwriter has represented and agreed that:

(a) it has only communicated or caused to be communicated and will only communicate or cause to be communicated an invitation or inducement to engage in investment activity (within the meaning of Section 21 of the Financial Services and Markets Act 2000 (the “FSMA”)) in connection with the issue or sale of the notes in circumstances in which Section 21(1) of the FSMA does not apply to us; and

(b) it has complied and will comply with all applicable provisions of the FSMA with respect to anything done by it in relation to the notes in, from or otherwise involving the United Kingdom.

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VALIDITY OF THE NOTES

The validity of the notes will be passed upon for us by Gibson, Dunn & Crutcher LLP, New York, New York. Mayer Brown LLP, New York, New York, will pass upon certain matters for the underwriters.

EXPERTS

Ernst & Young LLP, an independent registered public accounting firm, has audited our consolidated financial statements included in our Annual Report on Form 10-K for the year ended December 31, 2017, and the effectiveness of our internal control over financial reporting as of December 31, 2017, as set forth in their reports, which are incorporated by reference in this prospectus supplement and elsewhere in the registration statement. Our financial statements are incorporated by reference in reliance on Ernst & Young LLP’s reports, given on their authority as experts in accounting and auditing.

WHERE YOU CAN FIND MORE INFORMATION

This prospectus supplement is part of a registration statement (File No. 333-223608) we have filed with the SEC under the Securities Act. The registration statement, including the attached exhibits and schedules, contains additional relevant information about us and the securities described in this prospectus supplement. The SEC’s rules and regulations allow us to omit certain information included in the registration statement from this prospectus supplement. The registration statement may be inspected by anyone without charge at the SEC’s principal office at 100 F Street, N.E., Washington, D.C. 20549.

In addition, we file annual, quarterly, and special reports, proxy statements and other information with the SEC under the Exchange Act. You may read and copy this information at the following SEC location:

Public Reference Room

100 F Street, N.E.

Washington, D.C. 20549

You may also obtain copies of this information by mail from the SEC’s Public Reference Room, 100 F Street, N.E., Washington, D.C. 20549, at rates determined by the SEC. You may obtain information on the operation of the Public Reference Room by calling the SEC at (800) 732-0330. You may also inspect reports, proxy statements and other information that we have filed electronically with the SEC at the SEC’s website at http://www.sec.gov. These documents can also be inspected at the offices of the New York Stock Exchange, 11 Wall Street, New York, New York 10005.

The SEC’s rules allow us to “incorporate by reference” information into this prospectus supplement. This means that we can disclose important information to you by referring you to another document filed separately with the SEC. The information incorporated by reference is considered to be a part of this prospectus supplement. Any information incorporated by reference in this prospectus supplement that we file with the SEC after the date of this prospectus supplement will automatically update and supersede information contained in this prospectus supplement. Our SEC file number is 001-13300.

We are incorporating by reference in this prospectus supplement the documents listed below and any future filings that we make with the SEC under Section 13(a), 13(c), 14 or 15(d) of the Exchange Act prior to the termination of this offering, provided, however, that we are not incorporating by reference any information furnished (but not filed) under Item 2.02 or Item 7.01 of any Current Report on Form 8-K, except as specified below:

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You can obtain copies of documents incorporated by reference in this prospectus supplement, without charge, by requesting them in writing or by telephone from us at Capital One Financial Corporation, Investor Relations Department, 1680 Capital One Drive, McLean, Virginia 22102, telephone (703) 720-2455. You should rely only on the information incorporated by reference or provided in this prospectus supplement or the accompanying prospectus. We have not authorized anyone else to provide you with different information. We are not making an offer of these securities in any state where the offer is not permitted. You should not assume that the information in this prospectus supplement, the accompanying prospectus or any document incorporated by reference is accurate as of any date other than the date of the applicable document.

Our principal executive office is located at 1680 Capital One Drive, McLean, Virginia 22102 (telephone number (703) 720-1000). We maintain a website at www.capitalone.com. The information on our website is not part of this prospectus supplement nor is it incorporated by reference. Documents available on our website include: (i) our Code of Business Conduct and Ethics; (ii) our Corporate Governance Guidelines; and (iii) charters for the Audit, Risk, Compensation, and Governance and Nominating Committees of the Board of Directors.

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Capital One Financial Corporation

$             % Senior Notes Due 2021

$             % Senior Notes Due 2025

Prospectus Supplement

                    , 2018

Joint Book-Running Managers

BofA Merrill Lynch

J.P. Morgan

Morgan Stanley

RBC Capital Markets

Capital One Securities