The Tensas River is a river in Louisiana in the United States. The river, known as Tensas Bayou in its upper reaches, begins in East Carroll Parish in the northeast corner of the state and runs roughly southwest for 177 miles more or less in parallel with the Mississippi River. The Tensas River merges with the Ouachita River in Jonesville in Catahoula Parish to become the Black River, not to be confused with Black Lake in Natchitoches Parish in north central Louisiana.