She was born in Hartford, Cheshire and was educated at St. Winifrid's School, Eastbourne, Sussex. She became a popular actress from appearing in such films as Perfect Strangers (1945) (as a nurse) and The Seventh Veil (1945) (as a troubled concert pianist). She is perhaps best known to American audiences as Gregory Peck's long-suffering wife in Alfred Hitchcock's The Paradine Case (1947). She later produced a series of travel films. Her autobiography is entitled The Eighth Veil, an allusion to the film which made her a star in Britain. Todd was known as the "pocket Garbo" for her diminutive, blonde beauty.
Ann Todd married three times. Her first husband, Victor N. Malcolm, was a grandson of Lillie Langtry; she had a son with him named David Malcolm. Her second and third husbands (Nigel Tangye and David Lean) were first cousins. She had a daughter with Nigel Tangye called Ann Francesca Tangye. She married film director Lean in 1949 and starred in a number of his films, including The Passionate Friends (1949), Madeleine (1950) and The Sound Barrier (1952). Lean and Todd divorced in 1957.
Ann Todd died on 6 May 1993 from a stroke aged 84.