The 1973 Winston Western 500 was a NASCAR Winston Cup Series racing event that was held on January 21, 1973, at Riverside International Raceway in Riverside, California. There were 191 laps; which was very hardcore at a road course for the early-1970s. The time of the race was almost 5 hours long; which made it the equivalent of 2.5 regulation-length Formula One races. The race was won by Mark Donohue. It would be his only win of the season. It was AMC's first win in the Grand National/Winston Cup series as a manufacturer since April 1, 1951.