The North Fork Republican River is a 55.4 mi tributary of the Republican River. It flows eastward from a source in Yuma County, Colorado to just north of Haigler in Dundy County, Nebraska. There it joins with the Arikaree River to form the Republican River. The North Fork Republican River drains an area of 5086 sqmi, including 4449 sqmi, or 87.5%, in eastern Colorado, 575 sqmi, or 11.3%, in southwestern Nebraska, and 62 sqmi, or 1.2%, in northwestern Kansas. Use of water from the North Fork Republican River is governed by the Republican River Compact, a water agreement among the U.S. states of Colorado, Nebraska, and Kansas signed on 1942-12-31.