Montana Highway 40 is a short, 4.5 miles (7.2 km) long state highway in the west of the US state of Montana. The highway begins at U.S. Route 93 on the southern outskirts of Whitefish and extends eastwards in a roughly straight line to U.S. Route 2, west of Columbia Falls. Highway 40 forms the central part of the most-direct link between the two cities, allowing travel from the Hi-Line communities and Glacier National Park to the communities of the Columbia Valley in British Columbia without needing to detour south via Kalispell, Montana or north via the Crowsnest Pass between British Columbia and Alberta.

The entire route is in Flathead County.