Foyt was born in Houston, Texas. His father was a mechanic who owned and raced midget cars as a hobby, and he gave the young A.J. a toy racer with a lawnmower engine at age three. Foyt later recalled his certainty about his vocation from his first victory at age five. He frequently clashed with authority at school — on one occasion a teacher called to report his homework was covered with racing cars — and eventually dropped out of high school to work as a mechanic and concentrate on racing.
Foyt debuted at Indianapolis in 1958 and became one of the event's defining figures across four decades of competition. He qualified for the Indianapolis 500 a record 35 consecutive times and holds numerous career records at the race, including most times led (39), most laps driven, and most miles driven over a career. His four victories came in 1961, 1964, 1967, and 1977.
In 1961 he successfully defended his USAC points championship and won Indianapolis, beating Eddie Sachs by 8.28 seconds after Sachs was forced to pit to replace a tyre in the closing laps. The 1964 win came in a reliable Offenhauser-engined roadster, the race remembered primarily for the fiery second-lap crash that claimed the lives of Dave MacDonald and Eddie Sachs. In 1967, Foyt inherited the lead when the dominant STP-Paxton Turbocar driven by Parnelli Jones expired three laps from the end; Foyt navigated through a five-car accident in the final lap's fourth turn to take the flag. His fourth win in 1977 was perhaps the most dramatic: he ran out of fuel, fell far behind, then turned up his turbocharger boost to make up roughly 1.5 to 2 seconds per lap on Gordon Johncock, whose own engine failed before Foyt had fully closed the gap.
Foyt holds the USAC career wins record with 159 victories and the Indy car racing career wins record with 67.
Foyt won the 24 Hours of Le Mans in his only attempt, in 1967, partnered with Dan Gurney in a Ford GT40 Mk IV entered by Carroll Shelby. Pre-race commentary was sceptical of the pairing — Foyt as an oval specialist was said to be out of his depth on the road course — but he had already demonstrated his road course ability with a second place at the 12 Hours of Sebring earlier that year. When Gurney overslept during the race and missed a driver change, Foyt was forced to double-stint through the night and wound up driving nearly 18 hours of the 24. The car ran clockwise, set a new distance record of 388 laps, and won comfortably over the Ferraris.
Foyt was equally successful in stock car racing. He won the 1972 Daytona 500 and took seven NASCAR wins in total. He was the USAC stock car champion in 1968, 1978, and 1979. In January 1965 at Riverside, he was challenging Dan Gurney for the lead of the Motor Trend 500 when his brakes failed on Riverside's long downhill back straight; the car launched off an embankment and tumbled end-over-end several times. The trackside doctor initially pronounced him dead before he was revived by Parnelli Jones. Foyt suffered severe chest injuries, a broken back, and a fractured ankle and returned to racing.
In 1990, his car left the track at Road America in Elkhart Lake, severely injuring his legs and feet. After multiple surgeries and months of physiotherapy, he returned for the 1991 Indianapolis 500 and qualified second, then completed a 35th consecutive start in 1992.
From the mid-1960s Foyt began fielding cars for himself and other drivers, building his own Coyote chassis from 1966 to 1983. As a team owner after retirement, he was one of the few CART owners to embrace the new Indy Racing League on its arrival in 1996. His drivers Kenny Brack won the 1998 IRL title and the 1999 Indianapolis 500, putting Foyt in the winner's circle at Indianapolis for the fifth time.
Foyt has been inducted into numerous halls of fame, including the International Motorsports Hall of Fame (2000) and the Motorsports Hall of Fame of America (1989). In 1987 he set the closed-course speed record in an Oldsmobile Aerotech at 257.123 miles per hour on a test track near Fort Stockton, Texas. Smokey Yunick, the legendary NASCAR mechanic, wrote in his autobiography that "A.J. Foyt, I think, was the greatest race driver there ever has been in U.S. racing history."