The 1978 NASCAR Grand National Winston Cup Series was the 30th season of professional stock car racing in the United States and the 7th modern era NASCAR Cup series. The season began on Sunday, January 22 and ended on Sunday, November 19. Cale Yarborough driving the Junior Johnson #11 First National City Travelers Checks Oldsmobile won his then record third consecutive NASCAR Grand National Winston Cup Winston Cup. Ronnie Thomas was crowned NASCAR Rookie of the Year in a tight battle with Roger Hamby.

William Caleb "Cale" Yarborough was an American NASCAR Winston Cup Series driver and owner, businessman, farmer, and rancher. He was one of only two drivers in NASCAR history to win three consecutive championships, winning in 1976, 1977, and 1978. He was one of the preeminent stock car drivers from the 1960s to the 1980s and also competed in IndyCar events. His fame was such that a special model of the Mercury Cyclone Spoiler II was named after him.