The Little Mississippi River is a river in eastern Ontario, Canada. It is the outlet river of Weslemkoon Lake and ends in the York River which in turn empties into the Madawaska River, a tributary of the Ottawa River.
The river joins the York River where it flows through Conroy Marsh, a provincially significant wetland. At one time, this river was used to transport logs out of the pine forests to sawmills located downstream. A number of timber slides were built to transport logs through rapids along the river. Now, the river is used for recreational canoeing.