Wausau is a city in and the county seat of Marathon County, Wisconsin, United States, along the Wisconsin River. As of the 2020 census, it had a population of 39,994. It is the core city of the Wausau metropolitan area, which includes all of Marathon County and had a population of 138,013 in 2020. The city's suburbs include Schofield, Weston, Mosinee, Maine, Rib Mountain, Kronenwetter, and Rothschild.

The Wisconsin River is a tributary of the Mississippi River in the U.S. state of Wisconsin. At approximately 430 miles long, it is the state's longest river. The river's name was first recorded in 1673 by Jacques Marquette as "Meskousing", which is rooted in the Algonquian languages used by the area's Native American tribes. The river's original meaning is obscure, but French explorers who followed in the wake of Marquette later modified the name to "Ouisconsin", and so it appears on Guillaume de L'Isle's map. This was simplified to "Wisconsin" in the early 19th century, before being applied to Wisconsin Territory and finally the state of Wisconsin.