Thermopolis is the largest town in Hot Springs County, Wyoming, United States, and also the county seat. As of the 2010 U.S. Census, the town population was 3,009.
Thermopolis is Greek for Hot City. It is home to numerous natural hot springs, in which mineral-laden waters are heated by geothermal processes. The town is named for the hot springs located there.
The town claims the world's largest mineral hot spring, appropriately named "The Big Spring", as part of Wyoming's Hot Springs State Park. The springs are open to the public for free as part of an 1896 treaty signed with the Shoshone and Arapaho Indian tribes.
Dinosaur fossils were found on the Warm Springs Ranch in 1993, and the Wyoming Dinosaur Center was founded soon after.