Margot Kidder, who starred as the Lois Lane to Christopher Reeve’s Clark Kent in four “Superman” films in the late ’70s and ’80s, died Sunday at her home in Montana. She was 69.

The actress’s cause of death is unknown, and TMZ reports she is survived by one daughter.

Kidder, who reprised her role as Lane in three “Superman” sequels in addition to the 1978 original, was a longtime mental health advocate, as her battle with bipolar disorder played out in the public eye in the late ’90s.

The native Canadian maintained her acting career until her death, and recent credits include Rob Zombie’s “Halloween II” in 2009, as well as a series of Canadian films, including “The Neighborhood” and “The Red Maple Leaf.”

Before landing the gig that would go on to define her career, Kidder appeared in the 1973 cult thriller “Sisters” as Siamese twins, as well as two horror films — “Black Christmas” in 1974 and “The Amityville Horror” in 1979, as one half of the tortured married Lutz couple.

She scored the coveted role of Superman’s paramour Lane in 1976 after a lucky call earned her a screen test in front of director Richard Donner.

“I’d never read comics, so I didn’t know much about Superman,” she said in 2009. “But I read this very funny script, and I went in and did a couple scenes, and next thing I knew, I was being flown to England to screen-test, and that was that.”

Kidder has said signing on to the film also marked the end of her first marriage to novelist Thomas McGuane, the father of her only child, daughter Maggie, as he wanted her to be a “subservient writer’s wife.”

The film shot her to international fame — something she later called “the weirdest thing in the world.”

“I still get stopped for being Lois Lane, and I’m 60 and have two grandchildren,” she told The AV Club. “So it’s kind of weird.”

Kidder and Reeve reprised their roles as the famous duo three more times, in 1980’s “Superman II,” 1983’s “Superman III,” and 1987’s “Superman IV: The Quest for Peace.”

Outside of Krypton, Kidder maintained a steady stream of roles, including the 1981 film “Heartaches” and a 2002 Broadway gig in “The Vagina Monologues,” as well as appearances on TV shows in the 2000s, including “Law & Order: SVU,” “The L Word,” “Brothers & Sisters,” “Smallville” and “R.L. Stine’s The Haunting Hour,” which won her an Emmy in 2015.