"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.
"Unfaithful" was released by Def Jam Recordings on May 1, 2006, as the second single from the album. "Unfaithful" is a pop 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.
"Unfaithful" received mixed to positive reviews from critics; many praised its powerful balladry, but some criticized the lyrics. The song reached the top ten on the singles charts in 19 countries, including the UK Singles Chart, on which it became Rihanna's third top-ten single. "Unfaithful" peaked at number six on the US Billboard Hot 100 chart. It was certified platinum by the Recording Industry Association of America (RIAA), denoting shipments of over one million copies.
The song's accompanying music video was directed by Anthony Mandler and premiered in May 2006. It features Rihanna in a love triangle in which she struggles to choose between her romantic interest and her lover, and regrets having cheated on the former. Since its release, "Unfaithful" has become a staple of Rihanna's live performances.
In 2006, she performed it on award ceremonies such as the MOBO Awards and the World Music Awards. The song was on the set list of three of her major tours, Good Girl Gone Bad (2007–09), the Last Girl on Earth Tour (2010–11) and the Loud Tour (2011).