Campbell County is a county in the U.S. state of Wyoming. As of the 2020 United States Census, the population was 47,026, making it the third-most populous county in Wyoming. Its county seat is Gillette.
Campbell County comprises the Gillette, WY Micropolitan Statistical Area.
Campbell County was created in 1911 from land annexed from Crook and Weston Counties. It was named either for John Allen Campbell, a governor of the Wyoming Territory, or for Robert Campbell, an trapper and fur trader associated with William Henry Ashley.
According to the U.S. Census Bureau, the county has a total area of 4,807 square miles (12,450 km2), of which 4,803 square miles (12,440 km2) is land and 4.0 square miles (10 km2) (9.6%) is water.