She was born Catherine Conn in New Orleans. Her father was a gynecologist who died when she was 10; her mother was a daughter of the first Jewish mayor of Shreveport, Louisiana. Young Catherine was educated first in New Orleans, later in Switzerland, France, and in London, where she studied at the Royal Academy of Dramatic Arts.
Under the name Kitty Carlisle, she appeared on Broadway in several operettas and musical comedies, including Champagne Sec, Benjamin Britten's opera The Rape of Lucretia; and Anniversary Waltz. In 1984, she returned to Broadway for the last time, replacing Dina Merrill as Peggy Porterfield in the hit revival of Rodgers and Hart's On Your Toes.
Among her early films were Murder at the Vanities, A Night at the Opera (with the Marx Brothers), She Loves Me Not, and Here Is My Heart. She resumed her movie career late in life, appearing in Radio Days and Six Degrees of Separation.
In 1946, Carlisle married playwright and director Moss Hart, whom she had met when they worked together at the Bucks County Playhouse in New Hope, Pennsylvania. He died in 1961; the couple had two children, Christopher and Catherine, who survive their mother.
Mrs. Hart became a household name with her appearances as a panelist on TV's To Tell the Truth and What's My Line? A trained operatic soprano, she made her Metropolitan Opera debut on December 31, 1966 as Prince Orlofsky in Johann Strauss's Die Fledermaus, reprising the role 10 more times that season and returning in 1973 for four more performances.
She served as chair of the New York State Council of the Arts from 1976 to 1996, and she was also was a member of the boards of various New York City cultural institutions. In recent years, she performed in nightclubs around the country, including Feinstein's at the Regency, and was a frequent presence at openings, benefits, and other events.
At 8pm tonight, the marquee lights of Broadway theaters will be dimmed for one minute in memory of Mrs. Hart.