Castroville is a city in Medina County, Texas, United States. Its population was 2,954 at the 2020 census. Prior to 1893, Castroville was the first county seat of Medina County. Castroville was founded by Alsatian-Texans, who came to Texas during the German emigration period of the mid-1800s. Most Alsatians who came to Castroville spoke Alsatian. The Alsatian culture and language are still kept alive by the residents of Castroville.

Medina County is a county located in the U.S. state of Texas. As of the 2020 census, its population was 50,748. Its county seat is Hondo. The county is named for the Medina River. The extreme northern part of the county lies within the Edwards Plateau, which elevates into the Texas Hill Country. The Medina Dam, the fourth largest in the nation when completed in 1913, is listed on the National Register of Historic Places. The irrigation project, creating Medina Lake, was built by 1500 skilled workers who worked in shifts operating 24 hours a day to complete the dam in two years. Medina County is part of the San Antonio, TX Metropolitan Statistical Area.