"Losing My Mind" is a song written by Stephen Sondheim originally for the 1971 musical Follies for the character of a former showgirl, Sally Durant Plummer. The song became a popular Top ten hit for singer and actress Liza Minnelli in 1989 on the UK Singles chart and in Europe. "Losing My Mind" has been covered by many artists over the years.

"Losing My Mind" was first performed by Dorothy Collins in the role of "Sally Durant Plummer" in the original Broadway production of Follies. Other performers who have sung the song in later productions of Follies include Barbara Cook (1985), Julia McKenzie (1987), Donna McKechnie (1998), Judith Ivey (2001), Victoria Clark (2007), and Bernadette Peters (2011).

The song was written as a torch song for the character of Sally to sing in the "Loveland" portion of the musical. The song "expresses her preoccupation with Ben, her idealized lover...With infinite attention to detail, Sondheim leads Sally from sunrise to sleepless night, revealing that every second of her existence is defined by her longing...the number ...explores the extent to which she has lost herself in this make-believe world of undying desire." As originally staged, Sally comes onstage in a "clinging, beaded silver" dress, holding a microphone. The "cute" Sally from Phoenix "has become a languid torch singer." She repeats her lines, reflecting "the paralysis about which she sings...the phrase 'It's like I'm losing my mind' occurs no less than six times."

In the UK Singles Chart, the most successful version has been by American singer and actress Liza Minnelli, reaching number six. It was the lead single from her 1989 studio album, Results, produced by Pet Shop Boys and Julian Mendelsohn. The 12" release peaked at number eleven on the Billboard Maxi Singles Sales chart. It also peaked at number twenty-six on the American dance chart.

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