(Adds manager's statement, reaction)
LOS ANGELES, May 14 (Reuters) - Actress Margot Kidder, best known for playing Lois Lane in the "Superman" films in the 1970s and 1980s, has died at the age of 69, triggering affectionate tributes from Hollywood.
Kidder's manager Camilla Fluxman Pines said the actress died peacefully in her sleep on Sunday at her home in Livingston, Montana. The cause of death was not given.
Canadian-born Kidder appeared in more than 70 movies and TV shows, including "The Great Waldo Pepper," "The Amityville Horror" and the 2014 children's TV series "R.L. Stine's The Haunting Hour," for which she won an Emmy award.
Kidder began her acting career in her 20s and shot to international fame playing the intrepid reporter Lois Lane in 1978's "Superman," opposite Christopher Reeve, and in three sequels.
"Thank you for being the Lois Lane so many of us grew up with," DC Comics, the home of the "Superman" franchise, said on its Twitter account.
"Star Wars" actor Mark Hamill tweeted "on-screen she was magic. Off-screen she was one of the kindest, sweetest, most caring woman I've ever known."
Reeve died in 2004 from complications from a spinal cord injury in 1995. The Reeve Foundation, which funds research into such injuries, said it was saddened by Kidder's death, adding, "Fly high, our friend, shine bright."
Kidder was unable to work for two years after a serious car crash in 1990, and eventually became bankrupt. Six years later, she suffered a mental health breakdown and in a highly publicized episode she disappeared for four days and spent time as a homeless person. She was later diagnosed with bipolar disorder.
After her breakdown, acting work dried up for several years, but Kidder later re-emerged with a guest starring role in TV shows like "Smallville" and "The L Word" and on stage including a 2002 Broadway production of "The Vagina Monologues."
She also was a prominent political activist, campaigning against the Gulf War, energy fracking and in support of Democrat Bernie Sanders in the 2016 U.S. presidential election.
Kidder became an American citizen in 2005.
She was married three times, including a six-day union in 1979 with actor John Heard.