Fontaine's assistant, Susan Pfeiffer confirmed the actress' death of natural causes at her home in Carmel, California, the Hollywood Reporter said.
The star of the Hitchcock classics 'Suspicion' and 'Rebecca' famously won an Oscar in 1942 over her bitter rival -- her older sister Olivia de Havilland.
Joan de Beauvoir de Havilland was born in Tokyo in 1917, to British parents. Due to the ill health of her and Olivia, their mother, Lilian, moved them to California and pushed them into acting.
It was Hitchcock, with his penchant for "cool blondes", who brought Fontaine to the forefront when he cast her as the second Mrs de Winter in 'Rebecca' (1940), the director's American debut.
A year later, Hitchcock placed her opposite Cary Grant in 'Suspicion', and she won the Oscar for her turn as Lina McLaidlaw Aysgarth. She thus became the only actor to win an Oscar in a Hitchcock film.
Fontaine and her sister, who never really got along since childhood, finally stopped speaking to each other in the mid- '70s. Olivia, a two-time Oscar winner, is 97 and living in Paris.
In 1978, she published her autobiography, No Bed of Roses, which detailed her feud with her sister.
Fontaine was married and divorced four times.
In the '40s, she and William Dozier, the second of her four husbands, formed Rampart Productions. In 1939, Fontaine married British actor Brian Aherne, and they divorced in 1945. She was married to 'Batman' TV show producer Dozier from 1946-51, to producer Collier Young from 1952-61 and to journalist Alfred Wright Jr from 1964-69.
