Matamoros, officially known as Heroica Matamoros, is a city in the northeastern Mexican state of Tamaulipas, and the municipal seat of the homonymous municipality. It is on the southern bank of the Rio Grande, directly across the border from Brownsville, Texas, in the United States. Matamoros is the second largest city in the state of Tamaulipas. As of 2016, Matamoros had a population of 520,367. In addition, the Matamoros–Brownsville Metropolitan Area has a population of 1,387,985, making it the 4th largest metropolitan area on the Mexico–US border. Matamoros is the 39th largest city in Mexico and anchors the second largest metropolitan area in Tamaulipas.