The Flathead National Forest is a national forest in the western part of the U.S. state of Montana. The forest lies primarily in Flathead County, south of Glacier National Park. The forest covers 2,404,935 acres of which about 1 million acres (4,000 km2) is designated wilderness. It is named after the Flathead Native Americans who live in the area.

Flathead County is in the U.S. state of Montana. At the 2020 census, its population was 104,357, making it the state's fourth most populous county. Its county seat is Kalispell. Its numerical designation is 7. Its northern border is on the state's north border, making it contiguous with the Canada–US border, facing British Columbia.