Mercedes is a U.S. city in Hidalgo County, Texas. The population was 15,570 at the 2010 census. It is part of the McAllen–Edinburg–Mission and Reynosa–McAllen metropolitan areas.

Hidalgo County is located in the U.S. state of Texas. The county seat is Edinburg and the largest city is McAllen. The county is named for Miguel Hidalgo y Costilla, the priest who raised the call for Mexico's independence from Spain. It is located in the Rio Grande Valley of South Texas and is one of the fastest-growing counties in the United States. As of the 2020 census, its population was 870,781, making it the ninth-most populous county in Texas, and the most populous county outside of the counties in the Texas Triangle. Hidalgo County is designated by the U.S. Census Bureau as the McAllen–Edinburg–Mission metropolitan statistical area, which itself is part of the McAllen-Edinburg-Mission-Rio Grande City, Texas combined statistical area with neighboring Starr County.