"3" is a song recorded by American singer Britney Spears for her second greatest hits album, The Singles Collection (2009). It was written and produced by Max Martin and Shellback, with additional writing from Tiffany Amber. The song was released on October 2, 2009 by Jive Records, as the only single from The Singles Collection. "3" is an uptempo electropop song that features a heavy bassline and synthesizers, and lyrics that talk about threesomes, while referencing American folk-singing trio Peter, Paul and Mary during the chorus as sexual slang.

"3" received positive appreciation from contemporary music critics, with some reviewers calling it a classic Spears song. The song achieved commercial success by topping the charts in the United States and Canada, as well as reaching the top ten in many countries around the world, including Australia, Finland, Norway, Sweden and the United Kingdom. In the United States, the song debuted at number one in the Billboard Hot 100, becoming the first to debut at the top position in over three years and the first non-American Idol artist in eleven years to do so. "3" was also the fifteenth song in the history of Billboard to debut at number one.

An accompanying music video for "3", directed by Diane Martel, features Spears and her dancers in front of different black and white backgrounds. Martel described it as sexy and playful, while contemporary critics gave it positive reviews, complimenting its simplicity. A director's cut was leaked on December 15, 2009. Spears has performed "3" during the Femme Fatale Tour (2011) and her Las Vegas residency Britney: Piece of Me (2013-2015).

On July 12, 2009, Spears confirmed through her Twitter account that she had begun recording new material, stating she was going into the studio with Swedish songwriter and producer Max Martin, while she was in during the European leg of The Circus Starring Britney Spears. They had previously collaborated on earlier hits including "...Baby One More Time", "Oops!...I Did It Again", "Stronger" and "If U Seek Amy". "3" was written and produced by Martin and Shellback, while additional writing was done by Tiffany Amber. Spears recorded her vocals for the song with the producers at Maratone Studios. John Hanes was responsible for Spears' vocal editing on "3", which was later mixed by Serban Ghenea at MixStar Studios in Virginia Beach, Virginia. On September 23, 2009, Jive Records officially announced the release of a greatest hits titled The Singles Collection through Spears's official website, in celebration of Spears's ten-year anniversary in the music industry, also announcing the release of "3" as the lead single from the album. The artwork for the single was unveiled through Spears' official website on September 28, 2009. "3" was sent to radio stations on September 29, 2009, while being digitally released on October 2, 2009.

...
Wikipedia