Thermopolis is the largest town in, and the county seat of Hot Springs County, Wyoming, United States. As of the 2000 census, the town population was 3,172.
"Thermopolis" is from the Greek for "Hot City". It is home to numerous natural hot springs, in which mineral-laden waters are heated by geothermal processes. It claims the world's largest mineral hot spring as part of 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.
Thermopolis is located at 43°38′44″N 108°12′53″W / 43.64556°N 108.21472°W / 43.64556; -108.21472 (43.645667, -108.214641). Thermopolis is located near the northern end of the Wind River Canyon and Wedding of the Waters, where the north-flowing Wind River becomes the Bighorn. Thermopolis is ringed by mountains, with the Bridger Mountains are to the southeast, the Owl Creek Mountains are to the southwest, the Big Horn Mountains to the east and the southern Absaroka Range to the west. Thermopolis is the southern-most municipality in the Big Horn Basin.