The Moose Horn River is a 36.4 mi tributary of the Kettle River in eastern Minnesota, United States. It is part of the St. Croix River watershed, flowing eventually to the Mississippi River. It rises at the outlet of Wild River Lake, 7 mi southwest of the city of Cloquet, and flows southwest through Carlton County, roughly parallel to Interstate 35. The river passes the communities of Mahtowa, Barnum, and Moose Lake, ending at the Kettle River southwest of the city of Sturgeon Lake.