Barbara O'Neil was born in St. Louis, Missouri. She began her acting career in summer stock. In July 1931 Bretaigne Windust, Charles Leatherbee (the grandson of Charles Richard Crane), and Joshua Logan, the three directors of the University Players, a three-year old summer stock company at West Falmouth on Cape Cod, were looking for a leading lady for their repertory season that winter in Baltimore. At the suggestion of George Pierce Baker, they auditioned and hired O'Neil, one of his talented students at the Yale School of Drama. Romances born of the University Players led to three significant marriages: actress Margaret Sullavan to Henry Fonda for a few months in 1932, director/actor Joshua Logan's younger sister Mary Lee Logan to Charles Leatherbee, and Joshua Logan himself to Barbara O'Neil, which lasted only a brief period in the early 1940s. O'Neil never remarried.

In 1937, O'Neil debuted in the film Stella Dallas and in 1939 she was cast in the role of Ellen O'Hara, Scarlett O'Hara's mother, in Gone with the Wind, after the role was turned down by Lillian Gish. The following year, she appeared in All This and Heaven Too; she was nominated for the Academy Award for Best Supporting Actress for the role of the domineering and jealous Duchesse de Praslin.

Her later films include Shining Victory (1941), I Remember Mama (1948), and Otto Preminger's Whirlpool (1949) and The Nun's Story (1959).

O'Neil died from a heart attack at the age of 70 on September 3, 1980. [Source: Wikipedia]