Susan Kay Quatro (born June 3, 1950) is an American singer, bass guitarist, songwriter, and actress. In the 1970s, she scored a string of singles that found success in Europe and Australia, with both "Can the Can" (1973) and "Devil Gate Drive" (1974) reaching number one in several countries.

Quatro released her self-titled debut album in 1973. Since then, she has released 15 studio albums, 10 compilation albums, and one live album. Other songs, including "48 Crash", "Daytona Demon", "The Wild One", and "Your Mama Won't Like Me", also charted highly overseas. Following a recurring role as bass player Leather Tuscadero on the popular American sitcom Happy Days, her duet "Stumblin' In" with Smokie's lead singer Chris Norman reached number four in the US, her only song to chart in the top 40 in her homeland.

Between 1973 and 1980, Quatro was awarded six Bravo Ottos, an award given to musicians as voted in the German teen magazine Bravo. In 2010, she was voted into the Michigan Rock and Roll Legends online Hall of Fame. She is reported to have sold over 50 million records worldwide, and continues to perform live. Quatro's most recent studio album, Face to Face, was released in 2023 and follows the 2021 collaboration The Devil in Me with her son Richard Tuckey, who had already taken part in No Control in 2019. Quatro also remains active in radio broadcasting.

Quatro was born and raised in Detroit. Her father, Art, was a semiprofessional musician and worked at General Motors. Her paternal grandfather was an Italian immigrant to the US and her mother, Helen, was Hungarian and she died in 1992. Her family name of "Quattrocchi" ("four eyes", meaning "bespectacled") was shortened to Quatro. Quatro's family was living in Detroit when she was born. She has three sisters, a brother (Michael Quatro), and one older half-sister. Her parents fostered several other children while she was growing up. Quatro grew up to be an "extrovert but solitary," according to Philip Norman of The Sunday Times, and she only became close to her mother after leaving the US for Britain.

Her sister Arlene is the mother of actress Sherilyn Fenn. Her sister Patti joined Fanny, one of the earliest all-female rock bands to gain national attention. Her brother, Michael Quatro, is also a musician.

She was influenced at the age of six by seeing Elvis Presley perform on television. She has said that she had no direct female role models in music, but was inspired by Billie Holiday and liked the dress sense of Mary Weiss of the Shangri-Las "because she wore tight trousers and a waistcoat on top – she looked hot".

Quatro received formal training in playing classical piano and percussion—her first instrument was bongos. She taught herself how to play the bass, after her sister asked her to learn it for her first band, the Pleasure Seekers. Her father gave her a 1957 Fender Precision Bass guitar in 1964, which she still uses in the studio.

Quatro played drums or percussion from an early age as part of her father's jazz band, the Art Quatro Trio. Sources vary regarding whether her playing in the band began at the age of seven or eight, and whether the instrument she played was a drum kit or percussion (bongo or congas). Subsequently, she appeared on local television as a go-go dancer in a pop music series.