The 1940 Summer Olympics, officially known as the Games of the XII Olympiad, was a planned international multi-sport event scheduled to have been held from September 21 to October 6, 1940 in Tokyo City, Empire of Japan, and later rescheduled for July 20 to August 4, 1940 in Helsinki, Finland following the outbreak of the Second Sino-Japanese War in 1937. They were ultimately canceled because of World War II alongside the 1940 Winter Olympics in Sapporo, Empire of Japan, and were the third games to be canceled due to war.

The Summer Olympic Games, also known as the Games of the Olympiad, and often referred to as the Summer Olympics, is a major international multi-sport event normally held once every four years on leap years. The inaugural Games took place in 1896 in Athens, Greece, and the most recent Games were held in 2021 in Tokyo, Japan. The International Olympic Committee (IOC) is responsible for organising the Games and for overseeing the host city's preparations. The tradition of awarding medals began in 1904; in each Olympic event, gold medals are awarded for first place, silver medals for second place, and bronze medals for third place.The Winter Olympic Games were created out of the success of the Summer Olympic Games, which are regarded as the largest and most prestigious multi-sport international event in the world.