A plateau is a flat, elevated landform that rises sharply above the surrounding area on at least one side. It is a type of highland consisting of flat terrain that is raised sharply above the surrounding area on at least one side. Plateaus occur on every continent and can be formed through either volcanic or erosional processes, such as upwelling of volcanic magma, extrusion of lava, or erosion by water and glaciers. Plateaus can be classified according to their surrounding environment as intermontane, piedmont, or continental. Some plateaus, such as the Deccan plateau of central India, occur far from mountain ranges. Plateaus can be dissected (eroded) by rivers, which can create deep canyons, but their surfaces can be interrupted by deep canyons. Plateaus that have been severely eroded are known as dissected plateaus.

The high flat surface that defines a plateau can continue for hundreds or even thousands of kilometers, as in the case of the Plateau of Tibet. The Colorado Plateau is the largest plateau in North America, covering 336,700 km2 (130,000 mi2) in the Four Corners region of the southwestern United States. The Missouri Plateau, or Coteau du Missouri, is a plateau found where the Rocky Mountains meet the Great Plains of central-northwest United States. Meseta de Canquel is a volcanic plateau in Argentina.

Plateaus are sculpted by geologic forces that lift them up and the wind and rain that wear them down into mesas, buttes, and canyons. Monument Valley and the Grand Canyon, both icons of the American Southwest, were chiseled from the Colorado Plateau. The highest and biggest plateau on Earth, the Tibetan Plateau in East Asia, resulted from a collision between two tectonic plates about 55 million years ago. Many plateaus form as magma deep inside the Earth pushes toward the surface but fails to break through the crust.