Apollo 18 is the fourth studio album by American alternative rock duo They Might Be Giants. It was released in 1992 through Elektra Records and was named after the cancelled Apollo 18 mission that was scheduled to have followed Apollo 17. The album was also associated with International Space Year, for which They Might Be Giants were declared the official "musical ambassadors" by NASA.

The album marked the first conscious effort by John Linnell and John Flansburgh to branch out of their early sound, opting for more traditional rock rhythms and fuller arrangements. The duo adopted a backing band with live drums during the supporting tour. It was their last album recorded as a duo, and the band expanded to include a regular rhythm guitarist, bass player and saxophone player for their subsequent releases. Apollo 18 also includes the "Fingertips" suite, a series of twenty-one short songs, most under thirty seconds long. The album generated three singles, "The Statue Got Me High", "The Guitar (The Lion Sleeps Tonight)" and "I Palindrome I", although only the first charted.