Brownsville is a city in and the county seat of Cameron County in the U.S. state of Texas. It is on the western Gulf Coast in South Texas, adjacent to the border with Matamoros, Mexico. The city covers 145.2 sq mi, and had a population of 186,738 at the 2020 census. As of the 2020 US Census, it is the 139th-largest city in the United States and 18th-largest in Texas. It is part of the Matamoros–Brownsville metropolitan area.