The Ouachita River is a 605-mile-long (974 km) river that runs south and east through the U.S. states of Arkansas and Louisiana, joining the Tensas River to form the Black River near Jonesville, Louisiana. It is the 25th-longest river in the United States.

Arkansas is a landlocked state in the South Central region of the Southern United States. It borders Missouri to the north, Tennessee and Mississippi to the east, Louisiana to the south, Texas to the southwest, and Oklahoma to the west. Its name derives from the Osage language, and refers to their relatives, the Quapaw people. The state's diverse geography ranges from the mountainous regions of the Ozark and Ouachita Mountains, which make up the U.S. Interior Highlands, to the densely forested land in the south known as the Arkansas Timberlands, to the eastern lowlands along the Mississippi River and the Arkansas Delta.