Moiben River is one of the most important tributaries of River Nzoia. It's source is the Cherangany Hills in Elgeyo Marakwet County, and flows through Uasin Gishu County and Trans Nzoia County. Moiben, a town in Uasin Gishu County of Kenya, is named after the River. It forms the boundary between Uasin Gishu and Trans-Nzoia Counties.