Regional designations of Montana
The U.S state of Montana is a large geographical area (147,046 square miles (380,850 km2)) that includes portions of the Pacific Ocean, Gulf of Mexico and Hudson's Bay watersheds, is split by the Continental Divide and is approximately 545 miles (877 km) east to west along the Canadian border and 320 miles (510 km) north to south. Historically and officially, this large state has been divided up into a variety of distinct regions. Additionally, Montana is part of a number of larger federal government administrative regions. This is a List of regional designations (official and historical) of Montana.
 Historical designations
- Hi-Line, is a region of the Montana-Canadian border along which runs the main line of the Great Northern Railway and U.S. Highway 2.
- Many Glacier, is a region within Glacier National Park. The region is located north of the Going-to-the-Sun Road, on the east side of the park.
- Medicine Line, the name given the 49th parallel border between the U.S. and Canada between Lake of the Woods and the continental divide by Native Americans because of its seemingly magical ability to prevent U.S. soldiers from crossing it.
- The Flathead
- Two Medicine, is the collective name of a region located in the southeastern section of Glacier National Park.
 Official state regions
 Tourism regions
- Custer Country, comprising Big Horn, Carter, Custer, Dawson, Fallon, Golden Valley, Musselshell, Powder River, Prairie, Rosebud, Treasure, Wibaux, Yellowstone counties. Includes the Little Bighorn Battlefield National Monument.
- Glacier Country, comprising Flathead, Glacier, Granite, Lake, Lincoln, Mineral, Missoula, Ravalli, and Sanders counties. Includes Glacier National Park.
- Gold West Country, comprising Beaverhead, Broadwater, Deer Lodge, Jefferson, Lewis and Clark, Madison, Powell, and Silver Bow counties.
- Missouri River Country, comprising Daniel, Garfield, McCone, Phillips, Richland, Roosevelt, Sheridan, Valley counties. Includes major portions of the Montana Dinosaur Trail.
- Russell Country, comprising Blaine, Cascade, Chouteau, Fergus, Glacier, Hill, Liberty County, Montana, Meagher, Petroleum, Pondera, Toole, and Teton counties. The region is named for the influence on the area by cowboy artist Charles M. Russell.
- Yellowstone Country, comprising Carbon, Gallatin, Park, Stillwater and Sweet Grass counties. Includes northern and western gateways to Yellowstone National Park.
 Department of Fish, Wildlife and Parks regions
- Region 1, Northwest Montana, (Kalispell, Montana), includes Flathead Lake
- Region 2, West Central Montana, (Missoula, Montana), includes the Clark Fork, Blackfoot and Bitterroot rivers.
- Region 3, Southwest Montana, (Bozeman, Montana), includes the Madison, Gallatin, Jefferson, upper Missouri, upper Yellowstone, Beaverhead, and Big Hole rivers.
- Region 4, North Central Montana, (Great Falls, Montana), includes the lower Missouri and Smith rivers.
- Region 5, South Central Montana, (Billings, Montana), includes the Yellowstone, Stillwater, Bighorn, and Boulder rivers.
- Region 6, North East Montana, (Glasgow, Montana), includes Fort Peck Reservoir on the Missouri River.
- Region 7, South East Montana, (Miles City, Montana), includes the Missouri, Yellowstone and Tongue rivers.
 Federal government regions
 U.S. Fish and Wildlife Service
 Bureau of Indian Affairs agencies
- Blackfeet Agency, services the Blackfeet Indian Reservation in Glacier and Pondera Counties.
- Crow Agency, services the Crow Indian Reservation in Big Horn, Yellowstone, and Treasure counties.
- Fort Belknap Agency, services the Fort Belknap Indian Reservation in Blaine and Phillips counties.
- Fort Peck Agency, services the Fort Peck Indian Reservation in Roosevelt, Valley, Daniels, and Sheridan counties.  The agency administers off-reservation trust lands in Montana for the Turtle Mountain Indian Reservation.
- Northern Cheyenne Agency, services the Northern Cheyenne Indian Reservation in Rosebud and Big Horn counties.
- Rocky Boy's Agency, services the Rocky Boy Indian Reservation in Hill and Chouteau County. 
 Bureau of Land Management
- Billings office
- Butte office
- Dillon office
- Glasgow office
- Havre office
- Lewistown office
- Malta office
- Miles City office
- Missoula office
 National Weather Service
Montana is part of the Western Region of the U.S. Department of Commerce, National Oceanic and Atmospheric Administration's National Weather Service (NWS). The NWS maintains four regional offices in Montana.
- Great Falls
 Social Security Administration
 U.S. Army Corps of Engineers
- Vichorek, Daniel N. (1993). The Hi-Line, Profiles of a Montana Land. Helena, Montana: American World and Geographic Publishing. p. 7. ISBN 1-56037-021-1.
- Rees, Tony (2007). Arc of the Medicine Line-Mapping the World's Longest Undefended Border Across the Western Plains. Lincoln, NE: University of Nebraska Press. p. 5. ISBN 978-0-8032-1791-1.
- "Montana Official Travel Site-Regions". Retrieved 2011-06-07.
- "Custer Country, Montana". Retrieved 2011-06-13.
- "Glacier Country, Montana". Retrieved 2011-06-11.
- "Gold West Country Communities". Retrieved 2011-06-07.
- "Montana's Missouri River Country". Retrieved 2011-06-11.
- "Montana's Russell Country-Area Map". Retrieved 2011-06-07.
- "Montana's Yellowstone Country-Map of Region". Retrieved 2011-06-07.
- "Fish and Wildlife Regions". Montana Fish, Wildlife and Parks. Retrieved 2011-05-29.
- "FWP Region 1". Montana Fish, Wildlife and Parks. Retrieved 2011-05-31.
- "FWP Region 2". Montana Fish, Wildlife and Parks. Retrieved 2011-06-07.
- "FWP Region 3". Montana Fish, Wildlife and Parks. Retrieved 2011-06-07.
- "FWP Region 4". Montana Fish, Wildlife and Parks. Retrieved 2011-06-07.
- "FWP Region 5". Montana Fish, Wildlife and Parks. Retrieved 2011-06-10.
- "FWP Region 6". Montana Fish, Wildlife and Parks. Retrieved 2011-06-10.
- "FWP Region 7". Montana Fish, Wildlife and Parks. Retrieved 2011-06-10.
- "Mountain-Prairie Region". U.S. Fish and Wildlife Service. Retrieved 2011-05-29.
- "Indian Affairs-Rocky Mountain Region". U.S. Department of the Interior. Retrieved 2011-05-29.
- "Blackfeet Agency". Retrieved 2011-06-07.
- "Crow Agency". Retrieved 2011-06-07.
- "Fort Belknap Agency". Retrieved 2011-06-07.
- "Fort Peck Agency". Retrieved 2011-06-07.
- "Northern Cheyenne Agency". Retrieved 2011-06-07.
- "Rocky Boy's Agency". Retrieved 2011-06-07.
- "Montana-Dakotas". U.S. Department of Interior. Retrieved 2011-05-29.
- "NOAA NWS Offices and Centers". Retrieved 2011-06-07.
- "Denver Region". Social Security Administration. Retrieved 2011-06-11.
- "U.S. Army Corps of Engineers-Northwestern Division". Retrieved 2011-06-11.