"Unfaithful" is a song by Barbadian singer Rihanna from her second studio album A Girl like Me (2006). It was written by Shaffer "Ne-Yo" Smith with the song's producers Stargate. The song was released by Def Jam Recordings on May 1, 2006, as the second single from the album. "Unfaithful" is a pop, dancehall and R&B ballad and was inspired by the music of American rock band Evanescence. Originally titled "Murderer", the single speaks about a woman who regrets cheating on her partner.

Robyn Rihanna Fenty is a Barbadian singer, businesswoman, and actress, one of the most prominent recording artists of the 21st century. Rihanna signed with Def Jam Recordings in 2005 and found mainstream recognition following the release of her first two studio albums, Music of the Sun (2005) and A Girl Like Me (2006). Both influenced by Caribbean music, the albums quickly earned commercial success and peaked within the top ten on the US Billboard 200 chart. Her third album, Good Girl Gone Bad (2007), incorporated elements of dance-pop, and established her status as a prominent music industry icon. Its lead single "Umbrella" peaked atop the US Billboard Hot 100, won her first Grammy Award from three nominations, and remains one of the best-selling singles of all time.