Mercer is a town in southern Iron County, Wisconsin, United States. The population was 1,649 at the 2020 census. The census-designated place of Mercer and the unincorporated communities of Carter and Manitowish are located within the town. Mercer identifies itself as the "Loon Capital of the World" to promote tourism. A wildlife study found Mercer had the highest concentration of common loons in the world.