It's a bird! It's a plane! It's the most valuable comic book in the world!

A copy of the comic book that introduced the iconic Superman to the world became the world's most expensive comic book when it sold for $6 million at an auction.

According to Heritage Auctions, a copy of Action Comics No. 1, the 1938 comic book featuring the first appearance of Superman, sold for $6 million at an auction on Thursday.

The previous auction record was held by the CGC Near Mint+ 9.6 copy of Amazing Fantasy No. 15, featuring the debut of Spider-Man, that sold for $3.6 million at Heritage in September 2021.

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Action Comics No. 1 is hailed as the most important comic ever published, the auction house said.

Heritage Auction said that Superman remains "remarkably like" the current-day superhero.

In the comic book, Heritage Auction said that Superman faced off against "unjust imprisonment, spousal abuse, disarmament and drunken driving," according to author Les Daniels in Superman: The Complete History.

In a statement to Fox News Digital, Heritage Auctions Vice President Barry Sandoval said that this auction was "truly momentous."

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"This has been a truly momentous auction for Heritage and the hobby, and we expected no less. It was gratifying to see collectors respond so enthusiastically to so many of the significant items throughout this event, including Superman’s debut, the letter from his co-creator Jerry Siegel that outlined the Superman who might have been, and those milestone moments drawn by legendary creators," Sandoval said.

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"Records were set throughout the auction, which concludes Sunday, and history was made," he said.