VERITAS is a major ground-based gamma-ray observatory at the Fred Lawrence Whipple Observatory in southern Arizona, using four 12-meter telescopes to detect faint Cherenkov flashes produced when high-energy gamma rays strike Earth’s atmosphere. Developed from earlier work at the site, including the Whipple 10-meter telescope’s landmark 1989 detection of the Crab Nebula, VERITAS was conceived in the 1990s, began construction in 2003, and entered regular operation in 2007. Its stereoscopic array sharply improves measurements of incoming particles, and upgrades have increased its sensitivity. By 2020, it had detected 63 very high energy gamma-ray sources and become a leading western hemisphere instrument for studying extreme cosmic phenomena.