Thomas Fitzpatrick (1799-1854), American trapper, guide, and government agent for Native Americans, was one of the most prominent mountain men during the mid-19th century.

Thomas Fitzpatrick, one of eight children, was born in County Cavan, Ireland. Little is known about his early life, but by the time he was 17 he had arrived in the United States. In 1823 he accompanied William Ashley's fur trading expedition up the Missouri River, and he participated in the Arikara War that summer.

For the next 17 years Fitzpatrick and other trappers crisscrossed the Rocky Mountains and the central and northern plains searching for beaver. He worked for companies headed by Ashley and later by Jedediah Smith and others. In 1830 one company sold its business to Fitzpatrick, James Bridger, and three other trappers, who formed the Rocky Mountain Fur Company. Four years later the company was dissolved, although Fitzpatrick, Bridger, and Milton Sublette soon...