The Mobile River is located in southern Alabama in the United States. Formed out of the confluence of the Tombigbee and Alabama rivers, the approximately river drains an area of of Alabama, with a watershed extending into Mississippi, Georgia, and Tennessee. Its drainage basin is the fourth-largest of primary stream drainage basins entirely in the United States. The river has historically provided the principal navigational access for Alabama. Since construction of the Tennessee-Tombigbee Waterway, it also provides an alternative route into the Ohio River watershed.