Situated in southern North America at about 23° N and 102° W, Mexico comprises much of Middle America.Physiographically, the lands east of the Isthmus of Tehuantepec including the Yucatán Peninsula (which together comprise around 12% of the country's area) lie within Central America; geologically, the Trans-Mexican Volcanic Belt delimits the region on the north. Geopolitically, however, Mexico is commonly not considered a Central American country.

Mexico's total area is 1,972,550 km², making it the world's 14th largest country by total area, and includes approximately 6,000 km² of islands in the Pacific Ocean (including the remote Guadalupe Island and the Islas Revillagigedo), Gulf of Mexico, Caribbean Sea, and Gulf of California. On its north, Mexico shares a 3,141 km border with the United States. The meandering Río Bravo del Norte (known as the Rio Grande in the United States) defines the border from Ciudad Juárez east to the Gulf of Mexico. A series of natural and artificial markers delineate the United States-Mexican border west from Ciudad Juárez to the Pacific Ocean. On its south, Mexico shares an 871 km border with Guatemala and a 251 km border with Belize.