San Antonio is the seventh-most populated city in the United States and the second-most populous city in the state of Texas. It was the fastest growing of the top 10 largest cities in the United States from 2000 to 2010, and the second from 1990 to 2000. The city straddles South Texas and Central Texas and is on the southwestern corner of an urban megaregion known as the Texas Triangle.

San Antonio is the center of the San Antonio–New Braunfels Metropolitan Statistical Area. Commonly referred to as Greater San Antonio, the metropolitan area has a population of approximately 2.5 million. Growth along the Interstate 35 and Interstate 10 corridors to the north, west and east make it likely that the metropolitan area will continue to expand.

The city contains five 18th-century Spanish frontier missions, including The Alamo and San Antonio Missions National Historical Park. Other notable attractions include the River Walk, the Tower of the Americas, SeaWorld, the Alamo Bowl, and Marriage Island. Commercial entertainment includes Six Flags Fiesta Texas and Morgan's Wonderland amusement parks, and according to the San Antonio Convention and Visitors Bureau, the city is visited by about 32 million tourists a year. The city is home to the five-time NBA champion San Antonio Spurs and hosts the annual San Antonio Stock Show & Rodeo, one of the largest such events in the country.

The U.S. armed forces have numerous facilities in San Antonio: Fort Sam Houston, Lackland Air Force Base, Randolph Air Force Base (which constitute Joint Base San Antonio), and Lackland AFB/Kelly Field Annex, with Camp Bullis and Camp Stanley located outside the city. San Antonio is home to six Fortune 500 companies and the South Texas Medical Center, the only medical research and care provider in the South Texas region.