It's a copy of the first issue of Action Comics. The issue was published in 1938 and cost just 10 cents.
Wednesday, it set a record for the most money paid for a single comic book after selling for $2.16 million.
About 100 copies of Action Comics No. 1 are believed to be in existence, but only a handful of those are believed to be in good condition.
The buyer's name was not released.