The Pawnee River is a river in southwestern Kansas in the United States, about 198 miles (319 km) long. It is a tributary of the Arkansas River, which in turn is a branch of the Mississippi River.It rises in northwestern Gray County at an elevation of 2,835 feet (864 m), as the outflow of several agricultural drainage channels. For 20 miles (32 km) the river runs due north, before turning northeast near Ravanna.