Gardner spent several years playing undemanding bit parts in MGM Bs such as We Were Dancing, Joe Smith, American, Kid Glove Killer, Calling Dr. Gillespie (all 1942), Pilot No. 5, Hitler's Madman (both 1943), Swing Fever, Three Men in White, Maisie Goes to Reno (all 1944), and She Went to the Races (1945). She even appeared briefly in an MGM "Our Gang" short, Mighty Lak a Goat for which her scene was reportedly directed by thenhusband Mickey Rooney. In 1943 she was loaned to lowly Monogram Pictures to play the ingenue in Ghosts on the Loose aside from being mauled by the East Side Kids and ogled by Bela Lugosi, her responsibilities were minimal. It took another loan-out assignment, that of a femme fatale in Universal's Hemingway adaptation, The Killers (1946), to make audiences sit up and take notice. Her good reviews prompted MGM to try her opposite the King himself, Clark Gable, in The Hucksters (1947), in which she played a self-assured nightclub singer. Gardner acquitted herself nicely and was promoted to full-fledged stardom.
In most films, her presence was basically decorative, but she contributed memorable performances to Show Boat (1951, as Julie, the beautiful mulatto, for which she performed several Jerome Kern songs that made it to the soundtrack album but were redubbed for the film itself), Mogambo (1953, opposite Gable in this remake of his earlier success Red Dust with Gardner snagging an Oscar nomination for her interpretation of the tarttongued character played in the original by Jean Harlow), and Joseph L. Mankiewicz's The Barefoot Contessa (1954), in a part she seemed born to play, an earthy Spanish dancer who's transformed into a screen goddess-but destined never to find personal happiness.
In 1957, life imitated art once again. Gardner divorced singer Frank Sinatra that year (they had married in 1951 following a tempestuous courtship) and, after playing American expatriate Lady Brett Ashley in the film adaptation of The Sun Also Rises adopted her character's lifestyle and moved to Spain, where she was surrounded by adoring European jetsetters and matadors. Years of these hedonistic pursuits took their toll on her beauty; by the time she'd turned 50 she looked at least 10 years older. But as a mature, worldly actress, she delivered several interesting, multilayered performances. Her other husbands were actor Mickey Rooney (whom she wed shortly after joining Metro) and bandleader Artie Shaw.
In later years Gardner lived in London, but spent one season as a cast member of the TV series "Falcon Crest" (1985) and shortly before her death completed an autobiography, "Ava," which was published posthumously in 1990. More than one obituary declared her the most beautiful woman who ever stepped in front of a camera, and she was once in fact "voted" The Most Beautiful Woman in the World.