Mary Margaret O'Hara is a Canadian singer-songwriter, who has been hailed as one of the greatest cult heroines in rock music despite having released very few of her own recordings. She is the sister of comedic actress Catherine O'Hara.

O'Hara was a student at the Ontario College of Art and Design in Toronto, Ontario in the 1970s, and was involved in the music scene as a member of Toronto bands Songship and Go Deo Chorus.

In 1984, O'Hara signed a recording contract with Virgin Records, but her first album did not appear until 1988 because O'Hara's perfectionism and unconventional recording habits made the record difficult to complete. Andy Partridge of XTC was once scheduled to produce recordings with her, but abandoned the project after just one day because he couldn't cope with O'Hara's eccentricities.

In 1987, Michael Brook saw O'Hara in performance and was captivated by her unique style, and soon took on the job of producing O'Hara's attempts at an album.

When Miss America was finally released in 1988, O'Hara's excellent songwriting (a fusion of jazz, country, rock and pop), and her distinctive vocal style -- which can move from a pure, angelic croon to a loud wail in seconds -- quickly won her raves from critics and fellow musicians alike. It was hailed in many quarters as one of the best and most distinctive records of the decade, and has in fact made an appearance in some music magazines' polls of the best records of the 20th century.

In 1991, O'Hara followed up with a four-song EP of Christmas material.

Following the Christmas EP, O'Hara took on several acting roles and appeared as a vocalist on recordings by a variety of other artists, including Morrissey, Bruce Cockburn, Holly Cole, Meryn Cadell and The Henrys . She also contributed songs to a number of compilation albums, including tributes to Vic Chesnutt and Kurt Weill, and participated in a 1994 Christmas concert with Holly Cole, Rebecca Jenkins, Jane Siberry and Victoria Williams, which was released as the album Count Your Blessings.

However, she did not release a new recording under her own name until 2001, when she worked on the soundtrack to the Canadian film Apartment Hunting (in which she also acted.)