Jeremiah Johnson, played by Robert Redford, is a former soldier who is disillusioned with civilization and decides to become a hermit in the Rocky Mountains in the mid-1800s. He learns how to survive in the wilderness and makes a few friends, including a trapper named Chris Lapp and a Native American man named Paints His Shirt Red.
However, Jeremiah's peaceful existence is interrupted when he inadvertently kills a member of the Crow tribe while defending himself from a raid on his cabin. This leads to a long-standing vendetta between him and the Crow, who seek revenge for the death of their warrior.
Despite his efforts to avoid conflict, Jeremiah is forced to engage in several battles with the Crow, who are skilled and relentless fighters. He proves to be a worthy opponent, however, and earns their respect for his bravery and skill.
Along the way, Jeremiah also becomes involved with a woman named Swan, who is a widow with a young son. They develop a close relationship, but tragedy strikes when the family is attacked by the Crow and Swan and her son are killed.
Jeremiah ultimately decides to leave the mountains and return to civilization, realizing that he cannot continue to live alone and that his actions have had consequences for both himself and others. The film ends with him walking down a snowy mountain path, uncertain of his future but seemingly at peace with his past.