Gloria is a doter of Frank Stewart and Alice Deidrick Stewart. She had one brother, Thomas, who died as an infant in 1912 from meningitis. Her father died from complications of an automobile accident in 1919, and her mother remarried, to Fred Finch, a banker. Finch's son, Frank Finch, became Gloria's stepbrother and later a sportswriter for the Los Angeles Times.
Alice Finch later claimed Gloria's father was descended from the royal Stuarts of Scotland, but in fact Stuart changed the spelling of her last name herself, when she began her acting career, because she reportedly felt 'Stuart' fit better on a theater marquee.
She attended Santa Monica High School and graduated in 1927; she enrolled at the University of California at Berkeley but dropped out before she married Blair Gordon Newell, a sculptor, on June 21, 1930. Stuart was discovered at the Pasadena Playhouse, signed to a contract by Universal Studios, and was selected as one of the thirteen WAMPAS Baby Stars of 1932. As a glamorous blonde, she was quickly cast in a variety of films and became a favorite of director James Whale, starring in The Old Dark House, The Invisible Man, The Kiss Before the Mirror and Secrets of the Blue Room.
Stuart was a founding member of the Screen Actors Guild, but her career with Universal failed to gain momentum. She moved to 20th Century Fox, and by the end of the decade she had starred in more than forty films.
In 1934, Stuart divorced Newell, then married screenwriter Arthur Sheekman, who was Groucho Marx's closest friend and a writer of many Marx Brothers movies, on July 29 of that year. Their daughter, Sylvia, was born in 1935.
After a thirty-year break from acting, Stuart appeared on television for the first time in the 1975 television movie The Legend of Lizzie Borden. Her husband Arthur died in 1978, and over the next few years Stuart kept busy and appeared regularly on the small screen.
In 1983, Stuart became involved with Ward Ritchie, a printmaker and a close friend of her first husband, Blair Gordon Newell. The couple became reacquainted after more than 40 years and soon developed a romantic relationship. Ritchie taught her to print on his hand press, and Stuart soon became a fine printer and founded a private press under the name "Imprenta Glorias". Under her own imprint, Stuart has created several artist's books that are in the collections of the Metropolitan Museum, the Library of Congress, The Getty Research Institute, the Morgan Library, the Victoria and Albert Museum, the Bibliothèque nationale de France, and various private and university collections. She has bequeathed her press and collection of rare metal type to Mills College. Stuart and Ritchie lived together from 1983 until his death in 1996.
Stuart achieved a level of celebrity she had never experienced during her years as a Hollywood contract player when she was cast in Titanic as 100-year-old Rose DeWitt Bukater. She received her first Oscar nomination for Best Supporting Actress, and Golden Globe and Screen Actors Guild Award nominations. At age 87, Stuart became the oldest nominee ever for a competitive, non-honorary Oscar. Although the Oscar and the Golden Globe were won by Kim Basinger, Stuart tied with Basinger for the SAG Award.
On June 21, 2010 Stuart was honored by the Screen Actors Guild for her seventy years of service.