"Cecilia" is a song by American musical duo Simon & Garfunkel. It was released in April 1970 as the third single from the group's fifth studio album, Bridge over Troubled Water (1970). Written by Paul Simon, the song's origins lie in a late-night party, in which the duo and friends began banging on a piano bench. They recorded the sound with a tape recorder, employing reverb and matching the rhythm created by the machine. Simon later wrote the song's guitar line and lyrics on the subject of an untrustworthy lover.

The song was a hit single in the United States, peaking at number four on the Billboard Hot 100. On the Cash Box Top 100, it reached number one.

"Cecilia" also did well in Canada, Germany, the Netherlands, and Spain, where it reached number two, and also in Switzerland and Belgium, where it peaked at number three, although it failed to chart in the United Kingdom, where it was released as a single about six months after the album. It has been the subject of numerous cover versions, most notably by the singer Suggs, whose version featured the ragga duo, Louchie Lou & Michie One and reached number four in the United Kingdom in 1996.