Montana is the largest among the eight Rocky Mountain states. It is located in the northwestern US and is ranked fourth in size among the 50 states.

Montana covers a total area of 147,046 sq mi (380,849 sq km), of which 145,388 sq mi (376,555 sq km) is taken up by land and 1,658 sq mi (4,294 sq km) by inland water.

Montana is bounded by the Canadian provinces of British Columbia, Alberta, and Saskatchewan on the North; by North Dakota and South Dakota on the East; by Wyoming and Idaho on the South; and by Idaho on the West. The state's geographic center is in Fergus County, 12 mi (19 km) W of Lewistown.