The Archdiocese of San Antonio is a Latin Church archdiocese of the Catholic Church in the United States. It encompasses 27,841 square miles (72,110 km2) in the U.S. state of Texas. The Roman Catholic Archdiocese of San Antonio had a self-reported 2018 population of 796,954, up from 728,001 in 2014. The archdiocese includes the city of San Antonio and the following counties: Val Verde, Edwards, Real, Kerr, Gillespie, Kendall, Comal, Guadalupe, Gonzales, Uvalde, Kinney, Medina, Bexar, Wilson, Karnes, Frio, Atascosa, Bandera County, and the portion of McMullen County north of the Nueces River.

San Antonio, officially the City of San Antonio, is a city in the U.S. state of Texas and the most populous city in Greater San Antonio, the third-largest metropolitan area in Texas and the 24th-largest metropolitan area in the United States at 2.6 million people in 2020. It is the most populous city in and seat of Bexar County. The city is the seventh-most populous in the United States, the second-largest in the Southern United States, and the second-most populous in Texas after Houston.