Her manager, Mitch Clem, confirmed the death but did not provide a specific cause.

Ms. Johns’s effervescence and crackling husky voice — which she attributed to “slightly twisted” vocal cords that permitted the air to hit “the soprano and the contralto at the same time” — made her a distinctive presence in nearly 60 films, dozens of TV appearances and scores of theatrical productions.

Film historian David Shipman once described Ms. Johns, with her blend of sex appeal and quirky charm, as “one of the more entrancing heroines of the ’40s, one of the very few in British films who knew how to play comedy.” She became a top box office draw in England but found little pleasure in stardom, telling a reporter: “It is not a pleasant way of earning a living. . . . It has made me ill, exhausted and unhappy.”

She attributed the failure of at least one of her four marriages to the pressures of being a leading lady and, by the early 1960s, she settled into a long and varied career as a character actress, enlivening even middling fare with her offbeat charm.

Ms. Johns represented the fourth generation in a show business family. Her parents, who were touring in South Africa with a musical revue when she was born, settled in England, where Ms. Johns studied ballet so intensely that she earned a teaching certificate at age 10. Her china-blue eyes, her athleticism and her voice (“like honey over graham crackers,” one arts writer enthused) propelled her stage and film career.

After several juvenile on-screen roles, she achieved breakthrough stardom with “Miranda” (1948) as a fishtailed seductress whose flowing blond hair provides strategic cover of her upper body.

The film, a comic fantasy with a sexually forward heroine, was a commercial smash. Ms. Johns reprised the part in the 1954 Technicolor sequel, “Mad About Men,” and racked up a slew of credits in other films, few of any consequence. Yet Ms. Johns was usually singled out for spirited work, whether opposite Alec Guinness in the comic satire “The Promoter” (1952) or opposite Richard Todd in live-action Disney swashbucklers “The Sword and the Rose” and “Rob Roy” (both 1953).

In Hollywood, she played a comely maiden in “The Court Jester” (1956), a musical comedy set in medieval England and starring Danny Kaye. That same year, she and Hermione Gingold made brief appearances as “sporting ladies” — prostitutes — in the all-star vehicle “Around the World in 80 Days.”

She drew an Academy Award nomination for her supporting role as an earthy innkeeper in “The Sundowners” (1960), a drama set in the Australian outback with Robert Mitchum and Deborah Kerr.

“Mary Poppins” (1964) was a showcase for Julie Andrews as the singing English nursemaid, but Ms. Johns proved delightfully eccentric and a serviceable singer in the supporting part of the children’s mother, Mrs. Banks.

On television, Ms. Johns starred with Keith Andes in short-lived CBS sitcom “Glynis” (1963), about a husband-and-wife team of amateur sleuths, and she played the henchwoman Lady Penelope Peasoup on the 1960s series “Batman,” among other guest roles. She also slummed in low-grade horror movies, all the while maintaining a vigorous theatrical career.

The show that dominated her résumé was Sondheim and Hugh Wheeler’s “A Little Night Music” (1973), inspired by Ingmar Bergman’s droll romantic roundelay “Smiles of a Summer Night” (1955). Ms. Johns had been cast as the world-weary courtesan and actress Desiree Armfeldt on the basis of her acting strengths more than her voice.

Director and producer Harold Prince said that the day of a preview for a VIP audience, Sondheim came to work bleary-eyed after an all-nighter spent writing a song: “Send in the Clowns,” a bittersweet ballad about life’s missed chances. He and Ms. Johns “adored it,” Prince recalled to Sondheim biographer Meryle Secrest. “And, talk about the guts of a jailbird, Glynis said, ‘If you’ll put the lyrics on a piece of paper I’ll sing it in front of the audience today.’”

Sondheim later told Secrest he had tailored the song to what Secrest called Ms. Johns’s “small, silvery voice” and that “nobody can sing it as well as she.” Its word choice — from the well-known first line, “Isn’t it rich?” — made the most of her limits by forcing a breath after the “ch” sound.

In Sondheim’s judgment, professional singers who later recorded it — including Frank Sinatra and Judy Collins — were, in effect, too expert at smooth phrasing to capture its bitter essence.

The show, which ran 601 performances, garnered five other Tonys in addition to Ms. Johns’s win for best actress in a musical, including best musical. She later told the Associated Press that “Send in the Clowns” was “the greatest gift I’ve ever been given in the theater.”

Glynis Margaret Johns was born in Pretoria, South Africa, on Oct. 5, 1923. Her father was the Welsh-born actor Mervyn Johns. Her mother, Australian-born concert pianist Alys Steele-Payne, came from a family of entertainers.

After several theater roles in London, notably as a cruel student in Lillian Hellman’s “The Children’s Hour,” Ms. Johns was signed to a film contract and excelled as Ralph Richardson’s high-strung adolescent daughter in “South Riding” (1938). Her career received a major boost when she appeared with Laurence Olivier in “49th Parallel” (1941), as a young Canadian Hutterite villager who encounters stranded German U-boat crew members.

Ms. Johns played opposite her father as the daughter of a mysterious innkeeper in the ghost story “The Halfway House” (1944), and she brought a worldly zest to the role of a friend who helps liberate Kerr from the routine of married life in “Vacation From Marriage” (1945).

Among her later supporting roles, she lent a much-needed spark to “The Chapman Report” (1962), as a poetry-spouting housewife who propositions a football-playing Adonis only to find him a boorish lover. She also transcended the lifeless comedy “Lock Up Your Daughters!” (1969) as the gleefully lecherous Mrs. Squeezum.

In some of her final screen performances, she was the callous mother of Kevin Spacey in “The Ref” (1994) and a sweet grandmother in the Sandra Bullock romantic comedy “While You Were Sleeping” (1995).

Onstage, Ms. Johns made a strong impression in a 1956 Broadway revival of George Bernard Shaw’s “Major Barbara,” portraying the idealistic title character opposite Charles Laughton as her munitions-maker father, and as four long-suffering women in John Mortimer’s sex comedy “Come As You Are,” a London hit in 1970.

Her appearance with Rex Harrison and Stewart Granger in a 1989 Broadway revival of W. Somerset Maugham’s romantic comedy “The Circle” was seen by critics largely as a chance to catch the three veteran performers — “sly old foxes at play,” as Times reviewer Frank Rich noted.

Ms. Johns, who retired in her late 70s, admitted to not feeling like a “whole person” offstage, and colleagues described her as insecure and even frightened when not performing. Andes, her sitcom co-star, once told TV Guide: “Glynis is a whole crowd of people. You’re never sure which one you’ll meet from hour to hour.”

Her marriages were short-lived. Her first, to actor Anthony Forwood, took a startling turn when he left her for movie star Dirk Bogarde. Her later marriages to business executives David Foster and Cecil Henderson and author Elliott Arnold ended in divorce. A son from her first marriage, Gareth Forwood, died in 2007.

She had no immediate survivors.

“I became a professional at 12, so it’s always been my life,” Ms. Johns once told the Times, looking back on her time as an actress.

“Later on, I wanted to lead what I thought of as a ‘normal’ existence, but I soon found I wasn’t as normal away from the theater as in it,” she continued. “Acting is my highest form of intelligence, the time when I use the best part of my brain. I was always told, by my married friends, for example, that I could apply that intelligence to something else, some other aspect of living, but I can’t. I don’t have the same flair in other things.”