Piedras Negras Municipality is one of the 38 municipalities of Coahuila, in north-eastern Mexico. The municipal seat lies at Piedras Negras. The municipality covers an area of 914.2 km2 and is located on the international border between Mexico and the USA, here formed by the Río Bravo del Norte, adjacent to the U.S. state of Texas.

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.