"Last Friday Night (T.G.I.F.)" is a song by American singer Katy Perry from her third studio album, Teenage Dream. The song was produced by Dr. Luke and Max Martin, who also co-wrote the song with Perry and Bonnie McKee. Perry stated that she was inspired to write the track after a night of wild partying and streaking. It was released as the album's fifth single on June 6, 2011, by Capitol Records, with a remix featuring American rapper Missy Elliott released to US radio stations and digital retailers on August 8, 2011; this version was included in Teenage Dream: The Complete Confection edition. It is a dance-pop song with lyrics about drunken fun and debauchery. Some of the risqué lyrics are often censored in radio versions of the song.

Katheryn Elizabeth Hudson, known professionally as Katy Perry, is an American singer, songwriter, and television personality. She is known for her influence on modern pop music and her camp style, being dubbed the "Queen of Camp" by Vogue and Rolling Stone. At 16, Perry released a gospel record titled Katy Hudson (2001) under Red Hill Records, which was commercially unsuccessful. She moved to Los Angeles at 17 to venture into secular music, and later adopted the stage name "Katy Perry" from her mother's maiden name. She recorded an album while signed to Columbia Records, but was dropped before signing to Capitol Records.