Old River (Natchitoches Parish) is a series of interconnected, natural waterways totaling over 25 miles (40 km) in length in Natchitoches Parish, Louisiana. Its main channel runs along Louisiana Highway 1 from south of Natchitoches, Louisiana, to Colfax, Louisiana. The river is flanked by Interstate 49 on the west and the Red River of the South on the east, and is one of the many waterways on Isle Brevelle.