International Race of Champions (IROC) was a North American auto racing competition, created by Les Richter, Roger Penske and Mike Phelps, promoted as an American-motorsports equivalent of an all-star game. Despite its name, IROC was primarily associated with North American oval track racing.

Drivers raced identically-prepared stock cars set up by a single team of mechanics in an effort to make the race purely a test of driver ability. It was run with a small field of 12 invited drivers. It was created and developed in 1972 by David Lockton, the developer of the Ontario Motor Speedway, launched in 1973, with Mark Donohue being the first driver to win the championship, in 1974. The cars used that year were Porsche Carrera RSRs. Donohue's win in the fourth and last race of that season was his last win, as he died in a Formula One crash at the Österreichring in practice for the 1975 Austrian Grand Prix. The series was not run in 1981, 1982, or 1983.

In 2007, IROC could not find a sponsor and postponed the first two races, at Daytona and Texas. IROC went on hiatus in 2007 hoping to return with a sponsor in 2008, which did not happen. In March 2008, IROC auctioned off its tools, equipment, cars, and memorabilia, and went out of business. On January 8, 2024, Ray Evernham alongside Rob Kauffman announced the series would relaunch in 2024 with the intent of one race while exploring future opportunities afterwards.

The drivers invited were from a broad range of racing disciplines: IndyCar, NASCAR, sports car racing, and on occasion, sprint car racing. Criteria for invitation was very loose, but typically consisted of recent season champions of the respective series, and individual winners of big events (Indy, Daytona, etc.) It was occasionally rumored that a top NHRA drag racer would be invited and compete, but none ever did.

Due to its fundamental stock car formula, and the majority of racing being contested on ovals, the series was often dominated by NASCAR participants (which was the major criticism of the series). Also, in the small field of about a dozen cars, the share of NASCAR invitees grew over time; from just three drivers in the first season to seven in the final season. The last non-NASCAR based champion of the series was Al Unser Jr. in 1988. Although open-wheel car drivers had numerous successes, as of 2005^[update], drivers from road racing series had only won two races in the history of IROC. In some years, no sports car drivers competed.

Through 2003, IROC was also known for its rainbow of car colors being easily recognized from all other racing series. Car numbers were utilized for scoring purposes, but were not the primary means of identification. Instead, the driver's surname would appear on the door of the car. Exceptions were made when Mario and Michael Andretti raced in the same events. In those cases, their first name was used. The numbers would change from race to race, with the number 1 being given to the driver starting first, and so on. The colors would correspond to the numbers. Before the races, drivers were assigned via blind drawing, as was how the starting grid for the first race was determined. The finishing order of the race would be inverted for the second race's starting grid, while the reverse of the points standings determined races three and four's grids. Numbers were assigned by the starting position. After the first race, the numbers were assigned based on points standings.

In 2004, the alcoholic beverage company, Diageo became the series' title sponsor, utilising their Crown Royal brand whiskey, replacing True Value, and the procedure changed as well. Cars would be identically painted in white, with trim which could be changed to represent the driver's colors in his regular racing series. Also, a driver's number in IROC would be his regular number. Thus, Steve Kinser would use green trim with the No. 11, and Matt Kenseth's car featured yellow trim with No. 17.

The only exception to the numbering scheme involved the number 3. Following the death of Dale Earnhardt in the 2001 Daytona 500, IROC retired the use of No. 3. Any driver with that regular number would use No. 03 instead. Hélio Castroneves raced with No. 03, but the car kept red trim, in reflection of his IndyCar being red.