The Fawn River is a 55.4-mile-long (89.2 km) river in southwest Michigan and northeast Indiana in the United States. It flows into the St. Joseph River at (41°50′45″N85°40′02″W) in the city of Constantine, Michigan. The headwaters rise in a series of lakes and marshes in northern Steuben County, Indiana near Pokagon State Park, where it is known as "Crooked Creek" and "Little Fawn River". It flows west-northwest across the northeast corner of LaGrange County, Indiana and then over the state line across the southeast corner of Branch County, Michigan before entering St. Joseph County, Michigan. Passing to the south of Sturgis, Michigan, the river meanders across the state line a few more times before flowing north into Constantine.