A playa is a flat-floored bottom of an undrained desert basin that becomes at times a shallow lake. It is a dry, vegetation-free, flat area at the lowest part of an undrained desert basin, where ephemeral lakes form during wet periods, and is underlain by stratified clay, silt, and sand, and commonly, soluble salts. Playas occur in intermountain basins throughout the arid southwestern United States. They are among the flattest known landforms, and their slopes are generally less than 0.2 meters per kilometer. When filled with only a few centimeters of water, many kilometers of surface may be inundated.

Playas are rich in features and characteristics that can reveal information about climates, past and present. Many playas in the Mojave region were the location of lakes and marshes during the last glacial period. Today, they flood only after seasonal storms provide flashflood waters, or in some cases, springs discharge large quantities of groundwater onto the playa. Sediments are distributed across the surface of a playa by thin sheets of water that flow down slope, or by sediment entrained in standing water. Playas are not passive receptors of sediment as they were once believed to be. They serve as important sources of dust and salts, which are blown to the surrounding uplands.

Terminology is quite confused for playas because of many local names. A saline playa may be called a salt flat, salt marsh, salada, salar, salt pan, alkali flat, or salina. A salt-free playa may be termed a clay pan, hardpan, dry lake bed, or alkali flat.

In addition to its geological meaning, "playa" can also refer to a few other things, such as a municipality in Cuba, a Puerto Rican barrio, or a song by A Boogie wit da Hoodie.