"3" is a song by American pop singer Britney Spears, from her upcoming second greatest hits compilation, The Singles Collection. It was released as the lead single of the album on September 29, 2009 by Jive Records. The song was produced by Max Martin and Shellback while Spears was on tour in Sweden. "3" is an uptempo dance song, that features a heavy bassline and has influences of electropop and rave. Lyrically, the track is about threesomes.
The song received positive critical appreciation from contemporary critics. "3" has also achieved commercial success by topping charts in the United States and Canada, as well as reaching the top ten in many other countries. In the United States, the song debuted at number one on the Billboard Hot 100, breaking many of the chart records. The music video of the song was directed by Diane Martel and features Spears and her dancers in different black and white backgrounds.