Loretta Swit, the Emmy-winning actress who made the high-strung and relentlessly militaristic Maj. Margaret Houlihan human, dignified and, against all odds, sympathetic on the acclaimed television series “M*A*S*H,” died on Friday at her home in Manhattan. She was 87.

Her death was announced by her publicist, Harlan Boll.

In the Oscar-winning 1970 film “M*A*S*H,” directed by Robert Altman, Major Houlihan (whose blatantly sexist nickname was Hot Lips) was played by Sally Kellerman. When the movie became a CBS series, Ms. Swit stepped into the role and made it her own, adding heretofore unseen nuance. She was nominated 10 years in a row for the Emmy Award for best supporting actress in a comedy series, and she won twice, in 1980 and 1982.

“M*A*S*H,” which aired from 1972 through 1983 on CBS, was, like the movie that inspired it, set at a mobile Army hospital during the Korean War. Major Houlihan spent the first five seasons distracted by her open secret of an affair with the sniveling, very married Maj. Frank Burns (Larry Linville).

Around the time Major Burns returned to the United States, she married a handsome officer whom she had met in Tokyo. But he proved unfaithful, and she was soon divorced and newly dedicated to her career as the unit’s head nurse. In a post on social media, her “M*A*S*H” co-star Alan Alda wrote, “We celebrated the day the script came out listing her not as Hot Lips, but as Margaret.”

“It was the greatest time in my career,” Ms. Swit told the British newspaper The Guardian in 2001. Margaret’s ambition throughout the series was to be “the best damned nurse in Korea, and that motivated everything I did, even when it came to sex.” Major Houlihan did seem to be on a flirtatious first-name basis with every general who visited the camp.

As early as Season 2, her nemesis, Capt. Benjamin Franklin Pierce (Alan Alda) — better known as Hawkeye — saw her good side, referring to her as “nurse, friend and all-around good egg.” Col. Sherman T. Potter (Harry Morgan) called her “the finest nurse I’ve ever scrubbed with.”

The character only grew in perceived stature as the seasons passed, wrestling violent patients into submission and performing triage in her wedding dress.

Ms. Swit firmly believed that “if you’ve got a long-run series, then there’s always got to be room for growth,” she told The Toronto Star in 2010. “Of all the places you’d be inclined to grow, I certainly think somewhere you’re in danger every day and healing people every day would be just the right place.”

The show explored Major Houlihan’s feelings about her proud military heritage, as the daughter of a general who would have preferred a son. And it looked in on the night of passion — under enemy fire — that she and Captain Pierce shared and, as soon as the morning-after dust settled, never spoke of again.

Loretta Jane Szwed was born on Nov. 4, 1937, in Passaic, N.J., to Lester Szwed, a salesman, and Nellie (Kassack) Szwed.

After graduating from high school in Passaic, Loretta attended the Katharine Gibbs School in Montclair, N.J., and began a secretarial career. Her employers included Elsa Maxwell, the society hostess and gossip columnist.

But she was also preparing for an acting career; she enrolled in the American Academy of Dramatic Arts and studied with the director Gene Frankel.

“That’s kind of all I ever wanted to be,” she recalled in a 2004 Archive of American Television interview. She remembered going to two movie double features a day with her mother, separated only by a dinner break, when she was growing up.

She took voice lessons and dance lessons, but her parents were horrified by her choice of entertainment as an actual career. As Ms. Swit told The Toronto Star in 2010, after they saw her in a play at a small Greenwich Village theater, “My mother said to my father, ‘If you don’t stop her now, she may wind up doing this for the rest of her life.’”

Her Off Broadway debut was in Ibsen’s “An Enemy of the People” in 1961. She was the understudy for the lead female role in the national tour of the romantic comedy “Any Wednesday.”

She also appeared onstage in the musical “Mame,” in the comic role of Agnes Gooch, the lead character’s mousy secretary-nanny, who bursts out of her sheltered existence and comes home pregnant. She appeared alongside Celeste Holm on the national tour and Susan Hayward in the Las Vegas production.

Later in her career, she also appeared on Broadway with Ted Bessell in “Same Time, Next Year” (1975) as a chronic adulterer and in “The Mystery of Edwin Drood” (1985), replacing Cleo Laine.

Before“M*A*S*H,” Ms. Swit appeared on the television series “Mission: Impossible,” “Mannix,” “Gunsmoke” and “Hawaii Five-O,” all in 1970.

And she kept busy with other projects during the show’s run. She played an obnoxious gossip columnist in a body cast in Blake Edwards’s Hollywood farce “S.O.B.” (1981), with Julie Andrews and William Holden. She was a crime boss’s unfaithful wife in “Freebie and the Bean” (1974), with Alan Arkin and James Caan. She appeared in the television movies “Mirror, Mirror” (1979), “The Love Tapes” (1980) and “Games Mother Never Taught You” (1982). And she made an enemy (temporarily) of Miss Piggy when she guest-starred in a 1980 episode of “The Muppet Show.”

In 1981, she played Detective Christine Cagney in the pilot of the police series “Cagney & Lacey,” and she was set to take on the role for the run of the new show. But she was unable to get out of her commitment to “M*A*S*H,” and first Meg Foster (for six episodes) and then Sharon Gless ended up with the part instead.

After “M*A*S*H” ended, Ms. Swit played the president of the United States in the satirical British movie “Whoops Apocalypse” (1986). She also continued to be seen regularly on TV series, including “Murder, She Wrote” (1994) and “Burke’s Law” (1995). And she continued her stage career, appearing in regional theater, graduating to the title role in “Mame” and winning the Sarah Siddons Award in Chicago for her performance in “Shirley Valentine.”

She had planned to retire from acting after appearing in the 1998 comedy “Beach Movie,” but she returned to the screen two decades later in “Play the Flute” (2019), about a youth pastor with a wayward flock. It was her last movie.

In 1983, Ms. Swit married Dennis Holahan — an actor who was also a lawyer, and who coincidentally bore an approximation of her most famous character’s surname — after they appeared together in an episode during the final season of “M*A*S*H.” They divorced in 1995.

No immediate family members survive.

As for concerns like aging and mortality, she shrugged them off in an interview with The Express, the London newspaper, in 2020.

“I don’t think about the passage of time,” Ms. Swit said, “just what I’m doing with it.”