Tova Borgnine, the Norwegian-born cosmetics entrepreneur and home-shopping star who was known not just for selling beauty products but also for being the fifth wife and most enduring relationship of the actor Ernest Borgnine, died on Feb. 26 at her home in Chester County, Pa. She was 80.

Her death was announced by Michele Uram, president of Tova Beverly Hills, Ms. Borgnine’s company. She did not cite a cause.

Ms. Borgnine was a redheaded beauty with a makeup boutique that catered to Las Vegas showgirls in 1971 when she was introduced to Mr. Borgnine by Marty Allen, the bushy-haired comedian, though the much-married Mr. Borgnine was wary. “Forget it, I’m through with women,” he recalled telling Mr. Allen. (His third marriage, to Ethel Merman, whom he wooed with $10,000 worth of flowers, lasted but five weeks.) To be fair, Ms. Borgnine was thrice married when they met. Suffice to say they both had experience, and a match was made. The couple married in 1973.

“I never got married with the idea of getting divorced,” Mr. Borgnine told People magazine in 1981. “I always wanted a happy home.”

In 1997, when the Borgnines’ marriage had lasted longer than all four of Mr. Borgnine’s earlier ones put together, Ms. Borgnine published a book, “Being Married Happily Forever: 22 Secrets, 12 Strategies, and 8 Compromises.”

“Focus your attention on your husband,” she wrote, boiling down the book’s lessons. “He’s the lion; he’s the head of the pride, king of the jungle. Let him be the leader of your pack.” (Secret No. 6 declared, “Men can only think about one thing at a time.” And Secret No. 15 suggested, sagely, “Never talk about money after 10 p.m.”)

Ms. Borgnine was a firm believer in pre-feminist marital values, though she left the household chores to her husband, who was deeply domestic. He cooked and cleaned — a holdover from his military service, his son, Cristofer Borgnine, said — and liked to run his lines while vacuuming.

The Borgnines often said that another factor in their happy marriage was their careers, which kept them apart half the time. The distinctively craggy-faced Mr. Borgnine made over 100 films in a career of more than six decades: He played the murderous sergeant in “From Here to Eternity” and the title role, a gentle butcher, in the 1955 film “Marty,” for which he won an Oscar, though he was perhaps best known as the star of the 1960s World War II television comedy “McHale’s Navy,” in which he played the irreverent and lovable captain of a PT boat with an oddball crew.

Ms. Borgnine was a serial beauty entrepreneur who found success with an exotic skin care line that had a pedigreed back story. Worried that the dry desert air was making the Las Vegas showgirls who were her customers look older than their years, she set out to find an emollient to correct their skin. As the story goes, she pressed the actress Merle Oberon into revealing the secret to her dewy complexion, which turned out to be a mask based on an ancient Aztec formula involving cactus, made by a family in Mexico. Ms. Borgnine tracked the family down, and they agreed to sell her the formula.

But in the fall of 1976, before she had a proper company or had sorted out manufacturing and distribution, an item in a syndicated gossip column noted Mr. Borgnine’s own newly dewy complexion and plugged his wife’s cactus face mask. Within days, as the Borgnines told it, they had received hundreds of letters clamoring for the product, and checks totaling $56,000.

“It must have been a slow news day,” Ms. Borgnine liked to say.

The Borgnines pitched the new business together. They called it Tova 9, a play on their last name. Mr. Borgnine called himself “Guinea Pig No. 1” and often recalled his wife coaxing him to use her mask.

“So she says to me, ‘Honey, try it.’ I say, ‘Grumble, grumble.’ But I put the stuff on,” he told The Boston Globe in 1978. “So help me Hannah, I like the stuff.”

In an interview, Cristofer Borgnine confirmed that the tales were not apocryphal: He recalled regularly coming home and seeing his father reading the newspaper in the living room, his famous features frozen in a bright pink face mask.

Mr. Borgnine would go on to boast to reporters of his wife’s products: “I shave with it, shower with it, shampoo with it, clean my teeth with it and smooth my skin with it.” The soap lathered well in hard water, he said, and his friend Steve McQueen once took 60 bars on location. Burt Reynolds, an avid catalog shopper, was a customer. So were Elke Sommer and Charo. (Ms. Borgnine’s business was always mail order only.) In the early 1980s, she added a Burt Reynolds men’s line, created at his request.

“Skin has no sex,” Ms. Borgnine told a U.P.I. reporter in 1984, when her company’s sales reached $6 million. “It doesn’t even know if you’re male or female.”

Tove Traesnaes was born on Nov. 17, 1941, in Oslo. Her father was a graphic artist; her mother, Aase (Olsen) Traesnaes, was a translator.

Tove was 7 when her parents divorced, and she moved with her mother to New York City. She hoped to be an actress or a model, but she also learned makeup artistry. She opened a cosmetics boutique on the Jersey Shore called Tova’s Touch, and after two early marriages ended in divorce, she moved to Las Vegas to be with her mother. There, she ran makeup concessions in casino-hotels like Caesars Palace. She later changed her first name to Tova.

In addition to Cristofer Borgnine, her stepson, Ms. Borgnine is survived by a son, David Johnson; two stepdaughters, Sharon and Nancee Borgnine; and six grandchildren. Ernest Borgnine died in 2012.

Ms. Borgnine was an early star of QVC, the home shopping network. She joined in 1991 and sold her beauty line and her perfume, Tova Signature, there for the next three decades. Later, she also sold jewelry. Her pre-pandemic sales, Ms. Uram said, were between $15 million and $20 million a year.

Ms. Borgnine was a hypnotic, pitch-perfect pitchwoman. Hawking her new fragrance, Tova Night, one evening in 2016, she noted its effervescence — “like Champagne tickling your nose” — and its aphrodisiac qualities. “We have confirmed that seven children have been conceived with Tova Night,” she declared impishly, before adding a caveat: “We make no guarantees.”

She was a Margo Channing of late-night television, handily upstaging the chirpy co-hosts whose job it was to do the scut work, in this case interjecting at regular intervals that a bottle of Tova Night could be had for six easy payments of $6.50.

“Spray it around you, darling,” Ms. Borgnine instructed her young co-host that evening. “It’s called a Tova halo.”