Adobe, Spanish word for a sun-dried brick and for the clay soil from which the brick is made. Adobe soils are found in many arid and semi-arid regions worldwide, notably in North Africa, Mexico, and the south-western United States. In the western United States, adobe soils cover many thousands of square kilometres. Adobe has been used for thousands of years to build houses and other structures. For example, ancient Babylonians, ancient Egyptians, and some Native American cultures of North and South America used adobe.

Composed of a very fine mixture of clay, quartz, and other minerals, adobe can be moulded easily when moist, but when dry is so hard that ploughing is almost impossible. Adobe soils are very fertile when irrigated, yielding undiminished yearly harvests of grains, alfalfa, and other crops (see Irrigation). Combined with straw, adobe soils can be moulded into bricks that are baked in the sun for 7 to 14 days. Because the bricks disintegrate when wet, adobe bricks can be used only in regions of limited rainfall. Adobe structures often have eaves and stone foundations for protection against moisture.

Adobe structures are often associated with the Pueblo of North America, who built cliff dwellings and ovens made of adobe. Remains of their mud-brick communal villages still stand after centuries. Adobe is still used in some regions of the world, such as Mexico and the south-western region of the United States, where it is particularly popular in the city of Santa Fe in New Mexico.