Christopher Hart said his mother had been in and out of the hospital since contracting pneumonia over the Christmas holidays.
"She passed away peacefully" at home Tuesday night, said Hart. "She had such a wonderful life, and a great long run, it was a blessing."
She had been touring around the United States in her one-woman show "Here's to Life" until getting sick.
David Lewis, her longtime musical director, said: "The show was about everyone she had known: Irving Berlin, George Gershwin and her wonderful relationship with her husband, Moss Hart."
Hart had appeared for years on the popular game show "To Tell the Truth" as a celebrity panelist.
The entertainer was also a tireless advocate for the arts, serving 20 years on the New York State Council on the Arts. In 1991, she received the National Medal of Arts from the President George H.W. Bush.
Well known for her starring role as Rosa Castaldi in the 1935 movie "A Night at the Opera," her other film credits included: "She Loves Me Not" and "Here Is My Heart," both opposite Bing Crosby; Woody Allen's "Radio Days"; and "Six Degrees of Separation."
She began her acting career on Broadway in "Champagne Sec," and went on to appear in many other Broadway productions, including the 1984 revival of "On Your Toes."
She made her operatic debut at the Metropolitan Opera in 1967 in "Die Fledermaus," and created the role of Lucretia in the American premiere of Benjamin Britten's "Rape of Lucretia."
From 1956 to 1967, she appeared on the CBS prime-time game show "To Tell the Truth" with host Bud Collyer and fellow panelists such as Polly Bergen, Johnny Carson, Bill Cullen and Don Ameche. The show featured three contestants, all claiming to be the same person. The panelists asked them questions to determine which was telling the truth.
Hart's late husband was the Pulitzer Prize-winning playwright Moss Hart, who wrote "You Can't Take It With You" and "The Man Who Came to Dinner" with George S. Kaufman and won a Tony for directing "My Fair Lady" on Broadway.
Carlisle's film career began in 1934; in "Murder at the Vanities," she sings "Cocktails for Two," a song later made famous in a spoof version by Spike Jones.
"A Night at the Opera" the following year was the Marx Brothers' sixth film and their first for MGM, where they shifted after their career at Paramount sagged at the box office. MGM's Irving Thalberg added more romance to the Marxes' formula, bringing in Carlisle and Allan Jones to play the young opera singers in love, and the film became a huge hit.
Elegant and sophisticated then, and now - with hair, makeup and dress perfectly in place - Hart has been called a "great dame."
In a piece on CBS' "60 Minutes" in 2000, Marie Brenner, author of "Great Dames: What I Learned From Older Women," said: "A great dame is a soldier in high heels. ... They lived through the Depression. They lived through the war.
"They were tough, intelligent and brassy women," said Brenner, who described Hart as a great dame who "walks into a room, and the room lights up."
Discipline ruled Hart's success. She began every day with an exercise routine, even after she turned 90.
"I can do things a woman a fifth my age can't do. ... I do 40 leg lifts without stopping, And then I take my legs, I put them over my head, and I touch the floor behind me with my toes, and then very slowly I let myself down, touching every vertebra as I go," Hart told "60 Minutes."
Hart was born in New Orleans on Sept. 3, 1910. She attended the Sorbonne, the London School of Economics and the Royal Academy of Dramatic Art in London.
She and Hart married in 1946 and had a daughter, Catherine, in 1950. Her husband died in 1961 at age 57. In later years, she lived on the next block from Kaufman's daughter, Anne Kaufman Schneider, and the two would confer when a revival of a Kaufman-Hart play was in the offing.
She served on the state arts council from 1971 to 1996, including 20 years as its chairwoman. In 1988, she testified in Albany to a legislative committee amid complaints that the council had funded gay-oriented projects.
"We fund art," she said. "We are neutral as far as anyone else is concerned. We don't fund anyone's point of view."
Hart's special concern for women's role in society led to her appointment as chairwoman of the Statewide Conference of Women and later as special consultant to New York Gov. Nelson Rockefeller on women's opportunities. She also moderated a TV series called "Women on the Move."
She served on the board of Empire State College in New York and was an honorary trustee of the Metropolitan Museum of Art and the Museum of Modern Art.
Besides Christopher Hart, 59, a director, writer and producer, survivors include her daughter, Dr. Catherine Hart, and three grandchildren.
Funeral arrangements were incomplete. "We're working on a terrific memorial," said her son.