Coahuila is a state in Northeast Mexico that is divided into 38 municipalities. According to the 2020 Mexican census, Coahuila is the 15th most populous state with 3,146,771 inhabitants and the third largest by land area spanning 151,846.16 square kilometres (58,628.13 sq mi).

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.