Guardian of the Wilderness is a 1976 theatrical narrative film (often alternatively titled Mountain Man) directed by David O'Malley about the true story of Galen Clark, an explorer who successfully campaigned to have the Yosemite area set aside from commercial development, the original forerunner of the American national parks system. Clark was prompted by his dedication to preserving places like the Mariposa Grove of Giant Sequoias, which he discovered, from being destroyed by loggers. The cast features Denver Pyle as Galen Clark, John Dehner as legendary naturalist John Muir and Ford Rainey as Abraham Lincoln. Clark was eventually appointed Superintendent of Yosemite, a position in which he served for more than two decades during which he defined the concept of an American park ranger; his varied history with the valley ranged across 55 years.

A book written by Mark S. Rinehart in 2009 titled Abraham Lincoln on Screen: Fiction and Documentary Portrayals on Film and Television and published by McFarland & Company states that the sequence of the film involving Abraham Lincoln never took place nor did Clark ever travel to Washington D.C.

The film's supporting cast includes Ken Berry, Cheryl Miller, Norman Fell and Cliff Osmond. The screenplay was written by David O'Malley and Karen C. O'Malley from a story by the film's producer Charles E. Sellier Jr. loosely based on the actual events. The music was composed and conducted by John Cameron and the song "Yosemite Theme" features music by Bob Summers and lyrics by Penny Askey. The film was rated "G" and thereby deemed suitable for children, and was shot on location by cinematographer Henning Schellerup, edited by Sharron Miller, and released in the United States in December 1976 with a running time of 112 minutes.