Grayson's longtime companion and secretary, Sally Sherman, said Thursday that the actress died of natural causes.
Grayson also was professionally linked with Howard Keel, with whom she co-starred in three movies. With him, Grayson sang and acted as the riverboat belle Magnolia in "Show Boat" (1951); as a Parisian dress shop owner in "Lovely to Look At" (1952) -- in which she sang Jerome Kern's "Smoke Gets in Your Eyes" -- and as a high-strung actress in "Kiss Me Kate" (1953).
Later in their careers, Grayson and Keel performed together in nightclubs -- she was a coloratura soprano, he was a baritone -- and toured in summer stock.
Born as Zelma Kathryn Elisabeth Hedrick on Feb. 9, 1922, in Winston-Salem, N.C., she dreamed as a teen of becoming an opera star. She was discovered while singing on Eddie Cantor's radio show by MGM talent scouts on the lookout for the next Deanna Durbin.
After taking acting lessons, the curvaceous Grayson was cast in the "Andy Hardy" movies. She had an uncredited part in "Andy Hardy Gets Spring Fever" (1939), then played an ingenue in "Andy Hardy's Private Secretary" (1941), singing "Lucia" and "Voices of Spring." The next year, she appeared in "The Vanishing Virginian."
Her first leading role was in Abbott & Costello's remake of "Rio Rita" (1942), where she played the titular character in the loopy musical about a Texas Ranger.
During the '40s, she performed in such films as "Seven Sweethearts," "Thousands Cheer," "Anchors Aweigh" opposite Frank Sinatra and Gene Kelly, "Two Sisters From Boston," "Till the Clouds Roll By," "It Happened in Brooklyn," "The Kissing Bandit" and "That Midnight Kiss."
Before her star turn in "Show Boat" in 1951, Grayson appeared in two movies at the first part of the decade: "The Toast of New Orleans" with Mario Lanza and "Grounds for Marriage."
During the '50s, Grayson also sang and starred in "The Desert Song," based on a Sigmund Romberg operetta, and "So This Is Love," a musical biography of the opera star Grace Moore.
Grayson's final film appearance was in 1956 in Paramount's "The Vagabond King" a remake of the 1930 version in which Grayson performed the singing role originally done by Jeanette MacDonald.
When movie musicals fell out of favor in the early 1960s, she appeared on stage in several musicals, including "Camelot," and in operas including "La Boheme" and "Madam Butterfly."
She appeared and sang as a guest star on several TV variety shows, including "The Perry Como Show," "The Dean Martin Show" and "The Bob Hope Show." Grayson also did numerous dramatic turns on TV, guest-starring on such programs as "General Electric Theater," "Playhouse 90," "Lux Playhouse," "Baretta" and, most recently, in "Murder, She Wrote" in 1989.
Grayson was married twice: to actor John Shelton and later to actor-singer Johnnie Johnston. She had one daughter, Patricia Kathryn, with Johnston.
Sherman told the Associated Press that there will be no funeral service.
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