"1 Thing" is a song by American singer Amerie from her second studio album, Touch (2005). Written by Amerie and Rich Harrison and produced by the latter, the song is influenced by go-go rhythms and features a prominent sample of the Meters' 1970 funk recording of "Oh, Calcutta!", written by Stanley Walden. Its lyrics focus on an unidentified "thing" that fuels a romantic attraction.

The song was released as the album's lead single on January 18, 2005, and is the only single from the soundtrack to the 2005 romantic comedy film Hitch. "1 Thing" received acclaim from critics, and peaked at number eight on the US Billboard Hot 100 and number four in the United Kingdom, becoming Amerie's first top-10 single. Its digital download and ringtone releases were each certified gold by the Recording Industry Association of America (RIAA). A remix of "1 Thing" features rapper Eve.

The song earned Amerie a nomination for Best Female R&B Vocal Performance at the 2006 Grammy Awards, and was also nominated for Choice R&B/Hip-Hop Track at the 2005 Teen Choice Awards. It was later named the 22nd and 25th best song of the 2000s decade by Rolling Stone and Robert Christgau, respectively.