Marvin (Ted) Thin Elk, Sr. (August 14, 1919 – January 27, 1997) was a Sicangu Lakota Sioux actor who spent most of his life on the Rosebud Indian Reservation in South Dakota. Ted became very involved in the Sicangu Lakota community through his participation in the Lakota Treaty Council and membership in the Grey Eagle Society. Because of his involvement in the community, Ted Thin Elk was awarded the title of chief. At the age of 72 Ted was cast in his first role as Grandpa Sam Reaches in the film Thunderheart. For his work in the film, Ted Thin Elk was accorded a First Americans in the Arts Award in 1992, the first year the honor was awarded. Ted continued his acting career by participating in two more films, The Broken Chain and Walking Thunder, and a television mini-series, Heaven and Hell: North and South, Book III, before passing away in 1997.