Piedras Negras is a city and seat of the surrounding municipality of the same name in the Mexican state of Coahuila. It stands at the northeastern edge of Coahuila on the Mexico–United States border, across the Rio Grande from Eagle Pass in the U.S. state of Texas. In the 2015 census the city had a population of 163,595 inhabitants, while the metropolitan area had a population of 245,155 inhabitants. The Piedras Negras and the Eagle Pass areas are connected by the Eagle Pass–Piedras Negras International Bridge, Camino Real International Bridge, and the Union Pacific International Railroad Bridge.

Coahuila, formally Coahuila de Zaragoza, officially the Free and Sovereign State of Coahuila de Zaragoza, is one of the 32 states of Mexico.