Evelyn Keyes, one of the last surviving co-stars of “Gone With the Wind” and a popular film actress in the 1940s, died on July 4 at an assisted-living home in Montecito, Calif. She was 91.

Ms. Keyes died of cancer, said the producer Allan Glaser, a friend, who told The Associated Press that the announcement had been delayed until the death certificate was filed.

Ms. Keyes played the pouty Suellen O’Hara, whose sister Scarlett steals her longtime boyfriend and marries him just to pay the taxes on the plantation, in the Academy Award-winning 1939 movie classic. But in later years she became almost as well known for her first memoir, “Scarlett O’Hara’s Younger Sister,” as for any of her movie roles. The book, published in 1977, concentrated on her numerous marriages and love affairs with the mostly rich and famous.

She was quoted as saying, “I always took up with the man of the moment and there were many such moments.”

Her first husband (1938-40) was Barton Bainbridge, a businessman. After she left him, for the Budapest-born director Charles Vidor, he committed suicide. She and Mr. Vidor married in 1944, but divorced the next year. Her third husband was John Huston, the director, writer, producer and actor.

After her 1950 divorce from Huston, Ms. Keyes was the constant companion of the producer Mike Todd. He left her for Elizabeth Taylor in 1956. The next year Ms. Keyes married the bandleader Artie Shaw (whose ex-wives included Ava Gardner and Lana Turner). They separated in the 1970s, but did not divorce until 1985. After his death in 2004 she sued his estate and was awarded $1.42 million.

Ms. Keyes also had romances with Anthony Quinn, David Niven and Kirk Douglas, according to her book.

She made other notable films as well. In the heaven-and-earth fantasy “Here Comes Mr. Jordan” (1941), she played the love interest of Robert Montgomery. In “The Jolson Story”(1946), she played a character based on Ruby Keeler, opposite Larry Parks as Al Jolson.

Evelyn Keyes was born on Nov. 20, 1916, in Port Arthur, Tex. Her father died when she was 2, and she grew up living with her mother and her grandmother in Atlanta, where she took voice and dance lessons. Weekend dancing jobs paid for her train fare to Hollywood.

Ms. Keyes made her film debut in Cecil B. DeMille’s pirate picture “The Buccaneer” (1938), starring Fredric March. After six more movie roles, four of them uncredited, she was cast in “Gone With the Wind.”

After that she made two pictures, “The Lady in Question” and “Ladies in Retirement,”directed by Mr. Vidor. She starred in at least six with Glenn Ford, beginning with “The Adventures of Martin Eden” and ending with “Mr. Soft Touch.” “Mrs. Mike” (1949), a Canadian Mounties drama, was said to be one of her favorites.

Her last notable movie role was as the wife whose out-of-town trip makes it possible for Tom Ewell to flirt with Marilyn Monroe in Billy Wilder’s “Seven Year Itch” (1955). Her final film role was in “Wicked Stepmother” (1989), a horror fantasy with Bette Davis. Her final screen appearance was in a 1993 episode of the CBS series “Murder, She Wrote.”

The actor Tab Hunter, a close friend, has talked about making a film based on her autobiographical 1971 novel, “I Am a Billboard.” The tentative title is “Georgia Peach,” but Ms. Keyes did not identify with the South.

“I have no roots,” she told The New York Times in 1977. “I deliberately set out to destroy them, and I did. If there’s any such thing as a hometown for me, it’s Hollywood. I was formed here as an adult.”

Evelyn Keyes Shaw