Margot Kidder, who found fame as Lois Lane in the 1978 film "Superman," died Sunday at her home in Montana, her manager confirmed to CNN.
She was 69 years old.
Kidder died Sunday at her home in Montana
Tributes poured in Monday on social media
According to her manager, the actress died peacefully in her sleep.
Kidder starred opposite Christopher Reeve's Clark Kent and his alter ego Superman in the original film as well as the three sequels: "Superman II" in 1980, "Superman III" in 1983 and "Superman IV: The Quest for Peace" in 1987.
Reeve died in 2004 of complications from an infection, nine years after becoming a quadriplegic following a horse riding accident.
In 2016, Kidder told entertainment website Hey U Guys that her chemistry with Reeve was authentic "because we came from similar backgrounds and he looked like one of my brothers."
"So the energy we had was one of brother and sister, which was often bickering, that took the place of romantic energy," she said. "No one noticed the difference one from the other -- it worked. We didn't have to create a different reality."
Born in the Northwest Territories of Canada, she made her professional acting debut on the TV series "Wojeck" in 1969 and had her first film role in the 1968 Canadian movie "The Best Damn Fiddler from Calabogie to Kaladar."
Hollywood soon beckoned and a move to Los Angeles led to roles on TV shows including "McQueen," "Mod Squad" and "Nichols."
But playing scrappy reporter and Superman's love interest Lois Lane was her breakout role.
Kidder told Hey U Guys she thought the film would be a flop.
"Nothing prepares anyone for that sudden thing of being world famous, it was such a shock," she said. "It wasn't something I really liked or something I was very good at. I didn't realize how good the movie was until I seen it at the premier in Washington."
She also starred in "The Amityville Horror" in 1979 and worked steadily in television and on stage.
After three marriages and thousands of dollars in medical bills, Kidder found herself homeless in 1996 as she struggled with bipolar disorder.
Her story grabbed the hearts of fans and Hollywood with many reaching out to help Kidder, who eventually got back on her feet and went on to become a mental health advocate.
Tributes to the actress poured in on social media Monday.
Funeral arrangements are pending, according to Franzen-Davis Funeral Home and Crematory in Livingston, Montana.