Idaho is a landlocked state in the Mountain West subregion of the United States. It shares a small portion of the Canada–United States border to the north, with the province of British Columbia. It borders Montana and Wyoming to the east, Nevada and Utah to the south, and Washington and Oregon to the west. The state's capital and largest city is Boise. With an area of 83,569 square miles (216,440 km2), Idaho is the 14th largest state by land area. With a population of approximately 1.8 million, it ranks as the 13th least populous and the 7th least densely populated of the 50 U.S. states.

The Mountain states form one of the nine geographic divisions of the United States that are officially recognized by the United States Census Bureau. It is a subregion of the Western United States.