A "Captain America" comic has sold for $3.12 million in the US.
The issue, published in March 1941, was in very good condition, said the auction house Heritage Auctions in Dallas, Texas on Thursday.
Nothing was initially known about the buyer.
The cover shows superhero Steve Rogers, aka Captain America, in patriotic Stars and Stripes costume punching Adolf Hitler in the upper jaw.
Captain America has now joined the small ranks of superheroes whose early comic books fetched more than three million dollars at auction.
A 1962 Spider-Man book set the record for $3.6 million last September.
Heritage Auctions said it was the most expensive comic book ever sold at auction.
A few months earlier, the Superman booklet Action Comics No.
1" from 1938 went under the hammer for $3.25 million.