Margot Kidder, who is best known for her work in the original Superman films as Lois Lane, has died. She was 69. The actress and activist's passing was announced by the Franzen-Davis Funeral Home in Livingston, Montana, and later confirmed by her rep, Camilla Fluxman Pines, to The Hollywood Reporter. According to the funeral home, Kidder passed away on Sunday at her home in Livingston, Montana. No further details about the cause of death were given by either Franzen-Davis or Fluxman Pines.

Kidder shot to stardom after starring opposite Christopher Reeve's Clark Kent in 1978's Superman. She would play Lois Lane three more times, in Superman II (1980), Superman III (1983), and Superman IV: The Quest for Peace (1987). She also starred in famous '70s horror films such as Black Christmas and The Amityville Horror, and later made cameos on shows like Smallville, Law & Order: SVU, and The L Word. Her last film role, according to IMDB, was as Maggie in the 2017 drama film The Neighborhood.

Warner Bros/Everett Collection

Outside of her work in film and television, Kidder was also politically active. In 2011, she was arrested alongside fellow actress and activist Daryl Hannah outside of the White House for protesting the Keystone XL pipeline. Additionally, ahead of the 2016 presidential election, she threw a dinner in support of Bernie Sanders's run for president. Her activism extended to the mental health sector as well, with Vanity Fair reporting that Kidder devoted much of her life to serving as a mental health advocate who raised awareness by speaking candidly about her highly publicized experience with bipolar disorder.

According to CinemaBlend, Kidder leaves behind one daughter, Maggie McGuane, and two grandchildren. Though she was married and divorced three times, after Kidder's marriage to French director Philippe de Broca ended in the early 1980s, she never married again, describing herself to The Guardian in 2005 as "a grandmother with my dogs and nice friends here in the Rocky Mountains."