別府大分毎日マラソン
This was the 15th appearance of the event, which is one of 12 athletics events to have been held at every Summer Olympics. Returning runners from the 1960 marathon included defending champion Abebe Bikila of Ethiopia and ninth-place finisher Osvaldo Suárez of Argentina. Bikila was favored to repeat. Significant challengers were Toru Terasawa of Japan (who had taken the world record from Bikila at the 1963 Beppu-Ōita Marathon and held it until the 1963 Polytechnic Marathon), Leonard Edelen of the United States (who had held the world record from the 1963 Polytechnic to the 1964 Polytechnic), and Basil Heatley of Great Britain (the current world record, who had broken it at the 1964 Polytechnic).