Margaret Brooke Sullavan (May 16, 1911 - January 1, 1960) was an American actress.

She was born in Norfolk, Virginia, the daughter of a wealthy stockbroker. She made her Broadway debut in 1931. She married Henry Fonda on December 25 of that year. The marriage ended the following year, although Sullavan and Fonda remained lifelong friends. Her marriage to director William Wyler was equally brief. Her third marriage, to agent and producer Leland Hayward, lasted 13 years and produced three children. While married to Hayward, she worked less and less. Her last film role was in 1950.

Sullavan suffered from depression and a congenital hearing defect that grew worse as she grew older. She was found unconscious in a hotel room in New Haven, Connecticut from a barbiturate overdose on January 1, 1960. Her death was officially ruled an accident, but many think it was a suicide.

Her film debut came in 1933 in Only Yesterday. She also appeared in Little Man, What Now? , The Good Fairy , So Red the Rose , The Moon's Our Home , Next Time We Love , The Shopworn Angel , Three Comrades (for which she was nominated for the Academy Award for Best Actress), The Shop Around the Corner, The Mortal Storm, Appointment for Love and Cry Havoc . She co-starred frequently with James Stewart, with whom she and Fonda had acted in a stock company when they were all unknowns.

Her daughter, actress Brooke Hayward , wrote a memoir, Haywire, about her family. It was made into a television movie starring Lee Remick.

She has a star on the Hollywood Walk of Fame at 1751 Vine Street.