Seguin ( ) is a city in and the county seat of Guadalupe County, Texas, United States; as of the 2010 census, its population was 25,175, by 2019 its population was estimated to be 29,992. Its economy is primarily supported by a regional hospital, as well as the Schertz-Seguin Local Government Corporation water-utility, that supplies the surrounding Greater San Antonio areas from nearby aquifers as far as Gonzales County. Several dams in the surrounding area are governed by the main offices of the Guadalupe-Blanco River Authority, headquartered in downtown Seguin.