thumb|280px|An aerial view of the mouth of the Bad River (center) and adjacent wetlands in 2006
The Bad River is a river flowing to Lake Superior in northern Wisconsin in the United States. It flows for in Ashland County, draining an area of in portions of Ashland, Bayfield and Iron counties. The Bad River sloughs were designated a Ramsar Wetland of International Importance on February 2, 2012.
Course
The Bad River issues from the southwestern end of Caroline Lake, a shallow lake on the boundary of Ashland and Iron counties which drains an area of acidic peatlands to its east. The Bad River initially flows southwestwardly before turning generally to the north for most of its course, along which it passes through the city of Mellen, Copper Falls State Park, and the community of Odanah in the Bad River Indian Reservation.
The Bad River's largest tributary is the White River,
Variant names
The United States Board on Geographic Names issued a decision clarifying the Bad River's name and course in 1965. According to the Geographic Names Information System, the stream has also been known historically as: