The men's marathon race of the 1908 Summer Olympics took place in London on 24 July 1908. Johnny Hayes won after Dorando Pietri was disqualified for having received assistance before the finish line. For the first time in an Olympic marathon, the distance was 26 mi 385 yd (42.195 km), which would become the standard distance in 1921. 75 competitors entered the race, of whom 55 from 16 nations started, with 27 from 11 nations finishing. NOCs could enter up to 12 athletes. The United States and South Africa each won their first Olympic marathon medals.

John Joseph Hayes was an American athlete, a member of the Irish American Athletic Club, and winner of the marathon race at the 1908 Summer Olympics. Hayes' Olympic victory contributed to the early growth of long-distance running and marathoning in the United States. He was also the first man to win a marathon at the now official standard distance of 26 miles 385 yards when Olympic officials lengthened the distance to put the finish line in front of the Royal Box.