Abstract The Permian Basin region, as defined for this chapter, includes all of the Permian basins beneath the high plains of western Texas that lie south of the Red River and Matador Uplifts. It also extends westward into the Southern Rocky Mountain region to include the related Orogrande and Pedregosa Basins in New Mexico. In the central part of the region, surface exposures of the Tertiary Ogallala Formation and other post-Paleozoic strata hide the Paleozoic geology, which includes many anticlinal and faulted structures, sand and shale basins, carbonate banks and reefs marginal to basins, and extensive carbonate shelf areas. On these shelves, carbonates grade into evaporite deposits and eventually into continental clastics. Knowledge of this geology is primarily from wells drilled for oil and gas. Peripheral outcrops of these Paleozoic strata do exist and are important to the interpretation of Permian Basin geology, but many formations and rock facies are known only from the subsurface. With the exception of the two outlying New Mexico basins, petroleum geologists with extensive subsurface experience were selected to write the various parts of this chapter.