Margaret Julia “Marlo” Thomas (born November 21, 1937) is an American actress, who first achieved fame on the TV series That Girl in the 1960s.

Thomas was born in Detroit, Michigan, the daughter of Rose Marie (née Cassanti; 1914–2000) and Lebanese-American comedian Danny Thomas (1912–1991). Her brother Tony Thomas is a television and film producer, and her sister, Terre Thomas, is a former actress. Marlo Thomas was raised in Beverly Hills, California, and went by the nickname of Margie Thomas while attending school. She attended Marymount High School in Los Angeles. She graduated from the University of Southern California with a teaching degree and was a member of the sorority Kappa Alpha Theta.

Thomas began appearing as a regular on The Joey Bishop Show (1961-1962). She followed the series with guest shots on The Many Loves of Dobie Gillis, Ben Casey, My Favorite Martian, and Bonanza, but it was not until 1966 that she hit her professional stride as aspiring New York actress Ann Marie on the ABC sitcom That Girl. The series ran until 1971, garnering her a Golden Globe Award and four Emmy nominations. She was instrumental in the production of the TV special and record album Free to Be… You and Me.