IROC XXVII was the 27th season of the Crown Royal International Race of Champions, which began on Friday, February 14, 2003 at Daytona International Speedway. The roster included 12 drivers from five separate racing leagues. Mark Martin won the first race to tie an IROC record 11 career wins, tying him with Al Unser Jr. and Dale Earnhardt. Rookie Kurt Busch won in only his second start in race 2 after finishing second at Daytona. At Chicagoland, Mike Bliss became the first driver representing the Craftsman Truck Series to win a race in IROC competition. Jimmie Johnson won the final race of the year for his first career IROC victory. Kurt Busch clinched the title with his fourth-place showing in the race, as Mark Martin and Mike Bliss, his closest competitors, finished fifth and tenth, respectively. The roster of drivers and final points standings were as follows:

Race One (Daytona International Speedway)

Race Two (Talladega Superspeedway)

Race Three (Chicagoland Speedway)

Race Four (Indianapolis Motor Speedway)