The contiguous United States are the 48 U.S. states on the continent of North America that are south of Canada and north of Mexico, plus the District of Columbia. The term excludes the states of Alaska and Hawaii, and all off-shore U.S. territories and possessions, such as Puerto Rico.

Together, the 48 contiguous states and D.C. occupy a combined area of 3,119,884.69 square miles (8,080,464.3 km²). Of this, 2,959,064.44 square miles (7,663,941.7 km²) is land, comprising 83.65% of U.S. land area. Officially, 160,820.25 square miles (416,522.5 km²) is water area, comprising 62.66% of the nation's water area. Its 2000 census population was 279,583,437, comprising 99.35% of the nation's population. Its population density was 94.484 inhabitants/sq mi (36.480/km²), compared to 79.555/sq mi (30.716/km²) for the nation as a whole. The 2010 census population was 306,675,006, comprising 99.33% of the nation's population, and a density of 103.639 inhabitants/sq mi (40.015/km²), compared to 87.264/sq mi (33.692/km²) for the nation as a whole.