A Oglala Sioux Tribe spokeswoman said Means died Monday at his ranch in Porcupine, S.D. Means announced last year that he developed inoperable throat cancer. He had said that he was going to use traditional American Indian remedies instead of mainstream medical treatments.
Means helped lead the 1973 uprising at Wounded Knee. The American Indian Movement was founded in the late 1960s to protest the U.S. government's treatment of Native Americans.
The group was the subject of controversy due to its alleged involvement in the slaying of a tribe member and the several gun battles with federal officers during the 71-day occupation of Wounded Knee.
Means often avoided the media, but when he spoke out publicly, he remained steadfast in his defense of AIM. He denied the group ever promoted violence.
Means and AIM co-founder Dennis Banks were charged in 1974 for their role in the Wounded Knee uprising, but after a trial that lasted several months, a judge threw the charges out on grounds of government misconduct.
Means is also known as an actor for his roles in movies such as "The Last of the Mohicans" and "Natural Born Killers."
The Associated Press contributed to this report.