The Pecos pupfish (Cyprinodon pecosensis) is a species of Pupfish in the Cyprinodontidae family. It is endemic to the Pecos River watershed in eastern New Mexico and western Texas in the United States. As of the late 1990s, pure populations occurred in small reaches of the Pecos River and tributaries in Chaves and Eddy Counties of New Mexico; in scattered sinkholes, lakes, and saline springs in New Mexico; and in the upper reaches of the Salt Creek drainage in Culberson and Reeves Counties of Texas.