* Flathead Lake: Largest natural freshwater lake west of the Mississippi River.
* Lake Koocanusa: Reservoir formed by Libby Dam on the Kootenai River.
* Lake McDonald: Located in Glacier National Park.
* Lower Red Rock Lake: Located in the Beaverhead-Deerlodge National Forest.
* Lake Helena: Located in the city of Helena.
Rivers:
* Missouri River: Longest river in North America, flows through Montana for over 500 miles.
* Yellowstone River: Flows through Montana for over 600 miles.
* Clark Fork River: Flows through Montana for over 300 miles.
* Flathead River: Flows through Montana for over 200 miles.
* Kootenai River: Flows through Montana for over 100 miles.
Reservoirs:
* Lake Koocanusa: Reservoir formed by Libby Dam on the Kootenai River.
* Fort Peck Lake: Reservoir formed by the Fort Peck Dam on the Missouri River.
* Canyon Ferry Lake: Reservoir formed by the Canyon Ferry Dam on the Missouri River.
* Hauser Lake: Reservoir formed by the Hauser Dam on the Missouri River.
* Holter Lake: Reservoir formed by the Holter Dam on the Missouri River.