Heroica Matamoros is a city located in the northeastern Mexican state of Tamaulipas. It serves as the municipal seat of the homonymous municipality and is situated on the southern bank of the Rio Grande, directly across the border from Brownsville, Texas, in the United States.
The city is the second largest in the state of Tamaulipas and ranks as the 36th most populous city in Mexico. As of 2016, its population was 520,367. Matamoros anchors the second largest metropolitan area in Tamaulipas; combined with Brownsville, it forms the Matamoros–Brownsville Metropolitan Area, which has a population of 1,387,985 and is the fourth largest metropolitan area on the Mexico–US border.