Her children, Zak and Emily Hudson, said their "kind, hilarious" mother died in Los Angeles after a brief illness.
Williams worked with some of Hollywood's most elite directors before her move to television, appearing in George Cukor's 1972 Travels With My Aunt, George Lucas' 1973 American Graffiti and Francis Ford Coppola's The Conversation from 1974.
But she was best known for Laverne & Shirley, the Happy Days spin-off that ran on ABC from 1976 to 1983 that in its prime was among the most popular shows on TV.
Williams played the straitlaced Shirley Feeney to Marshall's more libertine Laverne DeFazio on the show about blue-collar roommates who toiled at a Milwaukee brewery in the 1950s and '60s.
The sitcom's opening became as popular as the show itself. Williams' and Marshall's chant of "schlemiel, schlimazel" as they skipped together became a cultural phenomenon and oft-invoked piece of nostalgia.
Marshall, whose brother, Garry Marshall, co-created the series, died in 2018.
Williams said in 2013 that she and Marshall had "very different personalities", but tales of the two clashing were "a bit overblown".
In 1982, Williams became pregnant and wanted shorter working hours. She walked off set and sued when her demands were not met, and appeared infrequently during the final season.
Williams was born one of two sisters in Los Angeles in 1947. She took up acting in high school and majored in theatre arts in college.
Her career began in 1969 with small TV roles including appearances on Room 222 and Love, American Style.
Her part in Lucas' American Graffiti would become a defining role. Happy Days, starring her Graffiti co-star Ron Howard, premiered the following year. The Laverne and Shirley characters made their first TV appearance as dates of Henry Winkler's Fonzie.
Lucas also considered her for Princess Leia in Star Wars, a role that went to Carrie Fisher.
In recent decades, Williams made guest appearances on dozens of TV series including 7th Heaven, 8 Simple Rules and Law & Order: Special Victims Unit.
Williams was married to singer Bill Hudson, who was father to her two children. He was previously married to Goldie Hawn and is also the father of actor Kate Hudson.
