Natrona County is a county in the U.S. state of Wyoming. As of the 2020 United States Census, the population was 79,955, making it the second-most populous county in Wyoming. Its county seat is Casper.

Wyoming is a landlocked state in the Mountain West subregion of the Western United States. It borders Montana to the north and northwest, South Dakota and Nebraska to the east, Idaho to the west, Utah to the southwest, and Colorado to the south. With a population of 576,851 in 2020, Wyoming is the least populous state despite being the 10th largest by area, with the second-lowest population density after Alaska. The state capital and most populous city is Cheyenne, which had a population of 65,132 in 2020.