Family spokesman Bob Palmer says Marvin died Friday morning of lung cancer at the Malibu home she shared with actor Dick Van Dyke, her partner of 30 years.
Marvin lived with Lee Marvin for six years and took his name. They broke up in 1970 and nine years later she sued for nearly $2 million, even though she had no alimony rights because the couple never married. Her lawyer dubbed the request "palimony" and the name stuck.
She eventually won $104,000, although the award was overturned.
The case set a precedent in California law that allowed unmarried partners to sue for financial support, and many similar cases followed.