West Texas is a vernacular term applied to a region in the southwestern United States that primarily encompasses the arid and semi-arid lands in the western portion of the state of Texas.

There is a general lack of consensus regarding the boundaries that separate East Texas and West Texas. Walter Prescott Webb, the American historian and geographer, suggested that the ninety-eighth meridian separates East and West Texas. The Texas writer A.C. Greene proposed that West Texas extends west of the Brazos River. Perhaps, the truth is that there is no distinct line that separates East and West Texas. Rather, there are places that are clearly in West Texas and there are places that are clearly in East Texas, and then there are places that fall within a transitional zone between these two regions.

West Texas is often subdivided according to distinct physiographic features. The portion of West Texas that lies west of the Pecos River is often referred to as "Far West Texas" or the "Trans-Pecos," a term first introduced in 1887 by the Texas geologist Robert T. Hill. The Trans-Pecos lies within the Chihuahuan Desert, the most arid portion of the state. Another important subdivision of West Texas is the Llano Estacado, a vast region of level high plains that extends into the Texas Panhandle. To the east of the Llano Estacado lies the “redbed country” of the Rolling Plains and to the south of the Llano Estacado lies the Edwards Plateau. The Rolling Plains and the Edwards Plateau subregions act as transitional zones between East and West Texas.