The Stillwater River rises 15 miles south of the border between Montana (United States) and Alberta (Canada), west of Glacier National Park in the Kootenai National Forest. It runs mainly south to Duck Lake, then Upper Stillwater Lake, Lagoni Lake and on to Lower Stillwater Lake. It then flows south to Kalispell where it joins the Whitefish River, very near where that river enters the Flathead River.

• List of rivers of Montana
• Montana Stream Access Law