Marvin, who had fought lung cancer for the last 18 months, died Friday at the Malibu home she shared with actor Dick Van Dyke, her companion of three decades, said a family friend, Bob Palmer.
Michelle Marvin, who legally changed her surname to Lee Marvin's even though they never married, made legal history in 1976 when the California Supreme Court ruled that she and other unmarried people could sue for property division when a relationship ended.
That decision paved the way three years later for an often-sensational 11-week trial in which Michelle Marvin was awarded $104,000 for what the judge called "rehabilitative purposes."
Both sides declared victory, but Michelle Marvin perhaps won the best sound bite: "If a man wants to leave his toothbrush at my house, he better bloody well marry me," she said after the 1979 trial.
An appeals court later blocked her from collecting the money, but the legal principle underlying her court battle was left intact. “Palimony” became a dictionary entry and grounds for a slew of cases involving celebrities and their former cohabiting lovers.
The so-called Marvin decision underscored the extent to which the sexual revolution of the 1960s had changed American society. Or, as Ruth Bader Ginsburg, later appointed to the U.S. Supreme Court, said in 1979 when she was a Columbia University law professor: "It illustrates the further breakdown of the legal line between married and unmarried union."
Michelle Marvin was born in Los Angeles on Nov. 13, 1933, and majored in theater arts at UCLA.
According to Palmer, she gained notice as a singer in the 1950s when she performed at a club on the Sunset Strip owned by Jerry Lewis.
She also danced in the 1958 Broadway production of "Flower Drum Song," directed by Gene Kelly.
She met Lee Marvin in 1964 when she had a bit part in the movie "Ship of Fools," which came out the next year. They began dating, and within a few months Marvin left his wife and began staying at Michelle's Hollywood apartment. In January 1965 they moved into a house he found for them in Malibu.
Later, she testified that Lee Marvin, who won an Academy Award for best actor in "Cat Ballou" (1965) during their relationship, had asked her to give up her career and said he would take care of her.
In May 1970 she legally added "Marvin" to her name, but the next month the actor had her evicted from the Malibu house. He married his childhood sweetheart, Pamela Feeley, in October of that year. In November 1971 he cut off a monthly allowance he had been paying to Michelle.
In February 1972, she took him to court.
With her attorney, the flamboyant Marvin Mitchelson, she calculated that her former boyfriend had earned $3.6 million during the six years of their cohabitation. She sued for half of that sum, $1.8 million. Mitchelson, who was already a famous celebrity divorce lawyer, said he intended to "put marriage on trial" in the Marvin case.
The Los Angeles County Superior Court trial was a tabloid dream.
Both Marvins took the stand, providing numerous moments of high drama. He said he never loved her; she said he proposed marriage twice. He said she threatened suicide; she said he made her pregnant three times and paid for one abortion. (One pregnancy ended in miscarriage, and two were terminated.)
Marvin, who said the second abortion left her unable to bear children, is survived by a sister, Diane Triola Johnson of Van Nuys.
In the end, Judge Arthur K. Marshall denied her $1.8-million claim, ruling that there was neither an express nor an implicit contract obligating the actor to share his wealth with her.