Though he became a familiar face in films and on US television over the past two decades, the identity that mattered most to the actor and singer Floyd Red Crow Westerman, who has died from leukaemia aged 71, was that of his Native American heritage. The causes he embraced included peace and the environment, but he saw both those issues as part of his cultural inheritance. Describing his early days as an activist in the American Indian Movement (AIM) he said simply: "We saw injustice going on and we wanted to stop it."
Westerman was born on the Lake Traverse reservation in South Dakota, home of the Sisseton-Wahpeton Dakota Sioux. Orphaned as a child, he was sent to a government boarding school, where speaking the Sioux language was discouraged. At school he met his friend Dennis Banks, who became a co-founder of AIM. After finishing high school on another reservation, Westerman studied theatre and education at Northern State College, in Aberdeen, South Dakota, and after graduation moved to Colorado.
He became a fixture in the Denver coffee-house scene, his deep voice making him a natural for country-edged music. He became close to Vine Deloria Jr, whose book, Custer Died for Your Sins, would become a bestseller. Offered a recording contract in New York, Westerman's 1970 debut album carried the same title as the book, and contained songs based on the same history. A second album, Indian Country, followed, and he toured campuses offering a combination concert and lecture that opened many eyes. He went on to record with Willie Nelson, Buffy Sainte-Marie, Kris Kristofferson and Jackson Browne.
In 1973, Westerman joined the AIM occupation of Wounded Knee, at the Pine Creek reservation, to protest against US government policies in the Black Hills. Two FBI agents were killed following a prolonged siege, and, although most AIM leaders, including Dennis Banks, were acquitted, AIM organiser Leonard Peltier was convicted.
Westerman's 1982 album, The Land is Your Mother, reflected the convergence of the interests of indigenous peoples worldwide and the environmental movement. He toured with Sting's rainforest tour in the early 1990s, and became involved in Harry Belafonte's campaign against the spread of nuclear power. But his musical success led to the movies. After starting with parts in TV shows such as MacGyver, he debuted on film playing Lou Diamond Phillips' father in Renegade (1989).
In 1990 he played the Sioux chief Ten Bears in the Oscar-winning Dances with Wolves, and the next year played the shaman who is Jim Morrison's spiritual guide in Oliver Stone's The Doors. He often described his career as following in the footsteps, and the parts, taken first by Will Sampson and then Chief Dan George. He was Sitting Bull in the TV mini-series Son of the Morning Star, and played a tribal elder in Richard Attenborough's Grey Owl (1999).
His greatest visibility came from recurring roles in a number of TV series, including, as Uncle Ray Firewalker in Walker Texas Ranger, and in the comedies Northern Exposure and Dharma and Greg. He achieved cult status as the codebreaker Albert Hosteen in The X Files, fond of reminding the audience that "something lives only as long as the last person who remembers it".
Westerman remained active politically, elected in 1999 as co-chair of the Coalition Against Racism in Sports, campaigning to change the nicknames of American teams such as the Redskins, Indians, and Braves. He described the invasion of Iraq as "just another land grab, like they did with Oklahoma and the midwest in America. Back then it was about land and gold and now it was about oil." Westerman also broadcast adverts for Lakota, a topical pain reliever, often wearing Native American dress and he continued to perform, as Chief Eagle Horn in Buffalo Bill's show in Hidalgo (2004), and in the television film The Tillamook Treasure (2006). His 2006 album, A Tribute to Johnny Cash, received a "Nammy" or Native American Grammy award, earlier this year.
Banks paid tribute to him, saying: "He was the greatest cultural ambassador that Indian America ever had - a real national treasure." He is survived by his wife, Rosie, a son and four daughters.
· Floyd Red Crow Westerman, actor, singer and activist, born August 17 1936; died December 13 2007