The Arkansas River is a major tributary of the Mississippi River. The Arkansas generally flows to the east and southeast, and traverses the states of Colorado, Kansas, Oklahoma, and Arkansas.

At 1,469 miles (2,364 km) it is the sixth longest river in the United States, the second-longest tributary in the Mississippi-Missouri system, and the 45th longest river in the world. Its origin is in the Colorado Rockies in Lake County near Leadville, and its outlet is at the historic site of Napoleon, Arkansas. The Arkansas River drainage basin covers nearly 195,000 sq mi (505,000 km²). (See watershed maps: spatial/maps_detail_static.cfm?map_select=391&theme=2" target="_blank">1) In terms of volume, the river is smaller than both the _Missouri and Ohio, with a mean discharge of 8,460 ft³/s (240 m³/s).