Bexar County is a county in the U.S. state of Texas. As of the 2010 census, the population was 1,714,773, and a 2013 estimate put the population at 1,817,610. It is the 17th-most populous county in the nation and the fourth-most populated in Texas. Its county seat is San Antonio, the second-most populous city in Texas and the seventh-largest city in the United States.