The Gallatin River is a tributary of the Missouri River, approximately 120 mi (193 km long), in the U.S. states of Wyoming and Montana. It is one of three rivers, along with the Jefferson and Madison, that converge near Three Forks, Montana, to form the Missouri.It rises in the northwest corner of Yellowstone National Park, in northwestern Wyoming, in the Gallatin Range of the Rocky Mountains.
The Gallatin River is an amazingly scenic river - winding through high alpine meadows, dropping into the rocky Gallatin Canyon, and flowing out into the Gallatin Valley. It is an exceptionally popular fly fishing destination for rainbow trout, brown trout and mountain whitefish. Portions of the river are designated as a Blue Ribbon trout stream while the remainder is designated Red Ribbon by the Montana Fish, Wildlife and Parks Department.