The Academy of Motion Picture Arts and Sciences announced her death on Monday in a post shared on Twitter.
The tweet, accompanied by an image of the Apache and Yaqui actress, read: “Sacheen Littlefeather, Native American civil rights activist who famously declined Marlon Brando’s 1973 Best Actor Academy Award, dies at 75.”
While no cause of death was immediately given, Littlefeather disclosed in a Facebook post in January last year that she had metastasized breast cancer.
Littlefeather made history when she stepped on stage at the 1973 Oscars on behalf of “The Godfather” star Brando, who decided to boycott the award ceremony in protest at the portrayal of Native Americans on the big screen. Brando was also reacting to the response of federal law enforcement to the occupation of the South Dakota town of Wounded Knee by members of the American Indian Movement.
Her short speech, for which she wore a buckskin dress and moccasins, was met with a mixture of boos and applause. It cost the budding actress, whose film credits included “Winterhawk,” “Shoot the Sun Down” and “The Trial of Billy Jack,” her career as she was soon blacklisted from the film industry and shunned by the entertainment world.
In August, the Academy formally apologized to Littlefeather for the mistreatment she experienced during her speech and in the years that followed.
A letter from former Academy President David Rubin to Littlefeather said the abuse she endured was “unwarranted and unjustified.”
He added: “The emotional burden you have lived through and the cost to your own career in our industry are irreparable. For too long the courage you showed has been unacknowledged. For this, we offer both our deepest apologies and our sincere admiration.”
Describing the apology as a “dream come true,” Littlefeather said: “We Indians are very patient people – it’s only been 50 years!
“We need to keep our sense of humor about this at all times. It’s our method of survival,” she added.
Last month, the Academy hosted an event at its film museum in Los Angeles that featured Littlefeather as a keynote speaker alongside other Indigenous performers.
CNN’s Scottie Andrew contributed to this report.