|Basin countries||Canada, United States|
|Source elevation||1,570 meters (5,150 ft)|
|Mouth elevation||875 meters (2,871 ft)|
|River system||Saskatchewan River|
The Belly River originates in northwestern Montana at Helen Lake, near the base of Ahern Peak in Glacier National Park. It flows north across the 49th parallel north into Alberta near Chief Mountain, in the east of the Waterton Lakes National Park. It continues north, being crossed by Highway 6 and Highway 5. It passes near the communities of Hill Spring and Glenwood, then turns northeast. It is crossed by Highway 2, then continues north along the base of the Mokowan Ridge, where it receives the waters of the Waterton River. Its flow becomes meandered before the river turns east around the Wild Turnip Hill, then it empties into the Oldman River west of Coalhurst, south of the Crowsnest Highway, at an elevation of 875 meters (2,871 ft).
From spring to mouth, the Belly River receives the following tributaries:
- North Belly River
- Mami Creek
- Dipping Vat Lake
- Bullhorn Coulee
- Layton Creek
- Waterton River
- McNab Coulee
- Geographical Names of Alberta. "Belly River". Retrieved 2009-03-22.
- Dawson, G.M., 1883. Preliminary report on the geology of the Bow and Belly river region, Northwest Territory, with special reference to the coal deposits. Geological Survey of Canada, Report of Progress for 1880-81-82, Part B.