“Hemisfair 1968,” widely known as HemisFair '68, was held in San Antonio, Texas, United States, from April 6 to October 6, 1968. Organized by San Antonio Fair, Inc., a nonprofit corporation, it was a special exhibition under the 1928 Paris Convention and marked the 250th anniversary of the city. It recorded 6,384,482 visits.

The idea took shape on January 28, 1962, when U.S. Representative Henry B. Gonzalez and department store executive William Sinkin discussed an exposition of the Americas for the anniversary. San Antonio Fair, Inc. received its state charter on December 29, 1962, and a 1963 feasibility study returned favorable results. After a favorable review by its classification committee on October 21, 1965, the International Exhibitions Bureau (Bureau International des Expositions, BIE) approved the Expo on November 17, 1965.

The theme, "The Confluence of Civilizations in the Americas," celebrated the cultures that had shaped the hemisphere and the city. The BIE counts 23 participants. The Expo opened two days after the assassination of Martin Luther King Jr., with First Lady Lady Bird Johnson as the featured speaker, and performers over the season included Louis Armstrong, Bill Cosby and Pat Boone.

Architects O'Neil Ford and Allison Peery oversaw the grounds on a downtown site southeast of the city center. Clearing it razed the diverse Germantown neighborhood, displacing 1,600 people and demolishing 1,349 structures, although an agreement preserved 20 historic homes. Funding combined a $30 million city bond, about $12.5 million from the Urban Renewal Agency, and state and federal money, and the Expo closed with a loss of $5.5 million. Ford designed the Tower of the Americas, which stands 622 feet high.

Several buildings remain. The Texas State Pavilion became the Institute of Texan Cultures, now part of the University of Texas at San Antonio; the Mexican Pavilion is the Instituto de Mexico; and the U.S. Pavilion houses the John H. Wood Federal Courthouse. The Henry B. González Convention Center occupies the northern edge of the 96-acre Hemisfair park. In 2009, the City Council created the Hemisfair Park Area Redevelopment Corporation, whose master plan has added new public spaces such as Yanaguana Garden, completed in 2015.

Civic leaders have credited Expo 1968 San Antonio with bringing the city into the modern era and helping it attract tourism and new employers, while UTSA historian David Johnson argues that other development efforts played larger roles. The Tower of the Americas remains its most visible legacy on the city skyline.