Belly River (Mont. and Alta.)

Belly River is a river in northwest Montana, United States and southern Alberta, Canada. It is a tributary of the Oldman River, itself a tributary of the South Saskatchewan River. The name of the river may come from the Blackfoot word mokowan of mokoan, meaning 'stomach'. The river was previously referred to as Mokowan River. Its Gros Ventre name is ʔinɔ́tɔnníícááh, also meaning 'belly river'. The river gives the name to the Cretaceous age Belly River Formation, which was observed on its banks by George Mercer Dawson in 1883.