Fremont County is a county in the U.S. state of Wyoming. In the 2010 census, 40,123 people lived there. Its capital is Lander. The county was formed in 1884. It is named for John C. Frémont, a general, explorer, and politician. It is about the size of the state of Vermont.

Fremont County includes the Riverton, Wyoming Micropolitan Statistical Area.