Canadian born “Superman” actress Margot Kidder has died at age 69, a Montana funeral home confirms.

Best known for playing Lois Lane opposite Christopher Reeve in the “Superman” films of the 1970s and 1980s, she went on to become an advocate for mental health issues after speaking out about living with bipolar disorder, including an infamous breakdown on the streets of Los Angeles in 1996. She credited a homeless man with showing compassion for her and saving her life during her “big, public flipout.”

“We are all … a breath away from mental illness, homelessness, all of these things we tend to so look down on,” she said in 2006.

“We are all one human family and we really have to take care of each other.”

Annie Kidder said her sister bore similarities to the tough-as-nails journalist she played in the “Superman” series.

“She was kind of an indomitable person,” she said in a phone interview. “She was a fighter. She was determined, outspoken.”

Annie Kidder said she does not know the cause of death at this time, and no funeral arrangements have been made.

“She was courageous about everything,” said Kidder, who is based in Toronto. “In struggling with her mental health, she was also determined that there shouldn’t be a stigma around that. It was important to be open about those things. There was nothing to be ashamed of.”

Margot Kidder continued to work in TV and film despite her struggles and won a daytime Emmy in 2015 for outstanding performance in a children’s or pre-school series for “R.L. Stine’s The Haunting Hour.” She also starred in films including “Black Christmas” and “The Amityville Horror” and TV series including CTV’s “Robson Arms.”

She also became a political activist in recent years and was among a group of environmentalists to be arrested outside the White House in 2011 during a protest against TransCanada’s Keystone XL pipeline.

Kidder, who became an American citizen, had settled in Montana to live in a “culture-free zone” away from the spotlight and close to her daughter and grandchildren.

Kidder was married and divorced three times and was also famously linked to former prime minister Pierre Elliott Trudeau. Kidder was credited with influencing Trudeau’s decision to launch a global peace initiative during his final months in office, according to the 2009 biography “Just Watch Me: The Life of Pierre Elliott Trudeau 1968-2000.”

Tributes to Kidder were posted to Twitter in the hours after her death began making headlines.

“She was a joy to be around,” wrote English actress Sarah Douglas, who co-starred alongside Kidder as supervillain Ursa in “Superman” and “Superman II.” “We continued to have fun together over the last 40 years.”

Actor and writer Kumail Nanjiani also tweeted about the actress’s impact on the film industry.

“RIP Margot Kidder. One of my favourite movies of hers is the original Black Christmas. It introduced some elements that are now genre tropes and she’s fantastic in it,” he wrote.

Both Kidder and Reeve, who played Superman, were relative unknowns when they got their leading parts, and neither saw many major roles afterward. Reeve died in 2004.