Mary Hansen is best known as the backup vocalist for the avant-garde British rock group Stereolab. Her first appearance in Stereolab's work is on the 1993 mini-album The Groop Played Space-Age Bachelor Pad Music, where she provides backup vocals for Laetitia Sadier. Outside of Stereolab, she also provided vocals for work by other groups including The High Llamas, Mouse on Mars and Moonshake. She also had a love for art and photography.

Mary Hansen was born on November 1, 1966 in the small town of Maryborough located 300km north of Brisbane, Australia. One of eight siblings, she showed an aptitude and love for singing from a young age. Her mother, an opera singer, personally trained Mary and encouraged her to follow her passion. Her skill won her several regional awards in Queensland vocal competitions.

After completing her initial schooling in Maryborough (as well as some tertiary study in Brisbane), she decided that she wished to travel abroad. After years of working and saving, she left for England in 1988 and quickly fell in with an Essex-based band called The Wolfhounds. The Wolfhounds would eventually play alongside a second Essex-based rock group called McCarthy, home to future co-founders of Stereolab Laetita Sadier and Tim Gane. After both McCarthy and the Wolfhounds disbanded in the early 1990s, Sadier and Gane asked Hansen to join Stereolab in 1992.

Hansen's effect on the group's music was immediately apparent. Her characteristic singsong backup vocals (as well as her ability to sing in both English and French) added a very unique and layered quality to Stereolab's already complex style of music. On subsequent albums, Hansen would continue to provide vocals (both backup and lead), but also played a larger role in forming the group's distinct sound by playing guitar, keyboard, and percussion. Outside of the studio, Hansen was known as a warm and witty personality if not a bit shy. Hansen typically eschewed the spotlight and let other band members act as the public face of the group.

Hansen was killed while cycling on December 9th, 2002 when her bicycle was hit by a truck in London. She was thirty-six years old. Stereolab's first album after her death, 2004's Margerine Eclipse, contained a track entitled Feel & Triple that was written as the group's tribute to Mary. A posthumously released 4-track EP entitled Hybrid that contains some of her recent solo work (as well as some of her own original artwork) was released by Duophonic Records in 2005.