Gianclaudio Giuseppe "Clay" Regazzoni (Italian pronunciation: [dʒaŋˈklaudjo dʒuˈzɛppe reɡatˈtsoːni]; 5 September 1939 – 15 December 2006) was a Swiss racing driver and broadcaster, who competed in Formula One from 1970 to 1980. Regazzoni was runner-up in the Formula One World Drivers' Championship in 1974 with Ferrari, and won five Grands Prix across 11 seasons.

Regazzoni competed in Formula One for 11 seasons, winning five Grands Prix. His first win was the Italian Grand Prix at Monza in his debut season, driving for Ferrari. He remained with the Italian team until 1972. After a single season with BRM, Regazzoni returned to Ferrari for a further three years from 1974 (where he was the runner-up to Emerson Fittipaldi) to 1976. After finally leaving Ferrari at the end of 1976, Regazzoni joined the Ensign and Shadow teams, before moving to Williams in 1979, where he took the British team's first ever Grand Prix victory, the 1979 British Grand Prix at Silverstone.

Regazzoni was replaced by Carlos Reutemann at Williams for 1980 and moved back to Ensign. Following an accident at the 1980 United States Grand Prix West, he was left paralyzed from the waist down, ending his career in Formula One. Regazzoni did not stop racing, and he competed in the Paris–Dakar rally and Sebring 12 Hours using a hand-controlled car during the late 1980s and early 1990s. In 1996, Regazzoni became a commentator for Italian TV. He was known as a hard-charging racer. Jody Scheckter stated that if "he'd been a cowboy he'd have been the one in the black hat". Regazzoni died in a car accident in Italy on 15 December 2006.