River Falls is a city in Pierce and St. Croix counties in the U.S. state of Wisconsin. It is mostly within the town of River Falls, and adjacent to the town of Kinnickinnic in St. Croix County. River Falls is the most populous city in Pierce County. The population was 16,182 at the 2020 census, with 12,546 residing in Pierce County and 3,636 in St. Croix County. It is part of the Minneapolis–St. Paul metropolitan area and about 30 miles (48 km) east of the center of that region.