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…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.