Wausau is a city in Marathon County, Wisconsin, United States, and its county seat. Located along the Wisconsin River, it had a population of 39,994 at the 2020 census, while the Wausau metropolitan statistical area including all of Marathon County had a population of 138,000. The city's suburbs include Schofield, Weston, Mosinee, Maine, Rib Mountain, Kronenwetter, and Rothschild.