Japan was the host nation of the 2020 Summer Olympics in Tokyo, originally scheduled to take place from 24 July to 9 August 2020 but postponed to 23 July to 8 August 2021 because of the COVID-19 pandemic. Since the nation's official debut in 1912, Japanese athletes have appeared at every Summer Olympic Games in the modern era, except for the 1948 Summer Olympics in London, to which they were not invited due to the nation's role in World War II, and the 1980 Summer Olympics in Moscow, as part of the United States-led boycott. The opening ceremony flag-bearers for Japan are basketball player Rui Hachimura and wrestler Yui Susaki. Karateka Ryo Kiyuna is the flag-bearer for the closing ceremony.
Qualification for Golf at the 2020 Summer Olympics in Tokyo was determined not by any form of qualifying tournament, but by the rankings maintained by the International Golf Federation.
Austria competed at the 2020 Summer Olympics in Tokyo. Originally scheduled to take place from 24 July to 9 August 2020, the Olympic Games were postponed to 23 July to 8 August 2021, because of the COVID-19 pandemic. It was the nation's twenty-eighth appearance at the Summer Olympics.
Slovenia competed at the 2020 Summer Olympics in Tokyo. Originally scheduled to take place from 24 July to 9 August 2020, the Games were postponed to 23 July to 8 August 2021, because of the COVID-19 pandemic. This was the nation's eighth consecutive appearance at the Summer Olympics as an independent nation. Slovenian athletes won five medals, including three gold, won by canoeist Benjamin Savšek, road racing cyclist Primož Roglič, and sport climber Janja Garnbret. Three gold medals is an all-time record for Slovenia at the Summer Olympics, having previously won two gold in 2000. The Olympics saw the debut of the men's basketball team who finished fourth in the tournament.
Argentina competed at the 2020 Summer Olympics in Tokyo. Originally scheduled to take place from 24 July to 9 August 2020, the Games were postponed to 23 July to 8 August 2021, because of the COVID-19 pandemic. Since the nation's official debut in 1900, Argentine athletes have competed in every edition of the Summer Olympic Games, except the 1904 Summer Olympics in St. Louis, the 1912 Summer Olympics in Stockholm, and the 1980 Summer Olympics in Moscow because of their support for the United States-led boycott.
Belgium competed at the 2020 Summer Olympics in Tokyo. Originally scheduled to take place from 24 July to 9 August 2020, the Games were postponed to 23 July to 8 August 2021, because of the COVID-19 pandemic. Since the nation's official debut in 1900, Belgian athletes have appeared in every edition of the Summer Olympic Games, with the exception of the 1904 Summer Olympics in St. Louis.
Poland competed at the 2020 Summer Olympics in Tokyo. Originally scheduled to take place from 24 July to 9 August 2020, the Games were postponed to 23 July to 8 August 2021, because of the COVID-19 pandemic. Since the nation's official debut in 1924, Polish athletes have appeared in every edition of the Summer Olympic Games, with the exception of the 1984 Summer Olympics in Los Angeles, because of the Soviet boycott.
India competed at the 2020 Summer Olympics in Tokyo, Japan. Originally scheduled to take place in July–August 2020, the games were postponed to 23 July to 8 August 2021, due to the COVID-19 pandemic. The Games marked the nation's 25th appearance at the Summer Olympics after having made its official debut at the 1900 Summer Olympics.
Slovakia competed at the 2020 Summer Olympics in Tokyo. Originally scheduled to take place from 24 July to 9 August 2020, the Games were postponed to 23 July to 8 August 2021, due to the COVID-19 pandemic. It was the nation's seventh consecutive appearance at the Summer Olympics after gaining its independence from the former Czechoslovakia.
Taiwan competed under the designated name "Chinese Taipei" at the 2020 Summer Olympics in Tokyo. Originally scheduled to take place from 24 July to 9 August 2020, the Games were postponed to 23 July to 8 August 2021, due to the COVID-19 pandemic. It was also the nation's tenth consecutive appearance at the Summer Olympics.
The team of the Olympic Federation of Ireland, which competed at the 2020 Summer Olympics in Tokyo, represented athletes from both the Republic of Ireland and those from Northern Ireland who choose it instead of the Great Britain and Northern Ireland team. Originally scheduled to take place from 24 July to 9 August 2020, the Games were postponed to 23 July to 8 August 2021, due to the COVID-19 pandemic. It was the team's twenty-second appearance at the Summer Olympics, having attended every edition since 1924 except the 1936 Summer Olympics in Germany.
Mexico competed at the 2020 Summer Olympics in Tokyo. Originally scheduled to take place from 24 July to 9 August 2020, the Games were postponed to 23 July to 8 August 2021, because of the COVID-19 pandemic. It was the nation's twenty-fourth appearance at the Summer Olympics. Athletes were given priority for vaccines in March.
Chile competed at the 2020 Summer Olympics in Tokyo. Originally scheduled to take place from 24 July to 9 August 2020, the Games were postponed to 23 July to 8 August 2021, because of the COVID-19 pandemic. Since the nation's debut in 1896, Chilean athletes have appeared in all but five editions of the Summer Olympics of the modern era. Chile did not attend the 1932 Summer Olympics in Los Angeles at the period of the worldwide Great Depression and was also part of the US-led boycott, when Moscow hosted the 1980 Summer Olympics.
Colombia competed at the 2020 Summer Olympics in Tokyo. Originally scheduled to take place from 24 July to 9 August 2020, the Games were postponed to 23 July to 8 August 2021, because of the COVID-19 pandemic. It was the nation's twentieth appearance at the Summer Olympics, with the exception of Helsinki 1952.
South Africa competed at the 2020 Summer Olympics in Tokyo. Originally scheduled to take place from 24 July to 9 August 2020, the Games were postponed to 23 July to 8 August 2021, because of the COVID-19 pandemic. It was the nation's eighth consecutive appearance at the Games in the post-apartheid era, and twentieth overall in Summer Olympic history.
Hong Kong competed at the 2020 Summer Olympics in Tokyo, Japan, marking the territory's seventeenth appearance at the Summer Olympics since its debut as a British colony in 1952. More medals were won at the 2020 Summer Olympics by athletes representing Hong Kong than ever before, and Hong Kong also won its first gold medal since the handover back to China.
Ecuador competed at the 2020 Summer Olympics in Tokyo. Originally scheduled to take place from 24 July to 9 August 2020, the Games were postponed to 23 July to 8 August 2021, because of the COVID-19 pandemic. It was the nation's fifteenth appearance at the Summer Olympics, and its most successful to date. The country won its third, fourth, and fifth ever medals, two golds and one silver, respectively, during the games.
Puerto Rico competed at the 2020 Summer Olympics in Tokyo. Originally scheduled to take place from 24 July to 9 August 2020, the Games were postponed to 23 July to 8 August 2021, because of the COVID-19 pandemic. It was the territory's nineteenth consecutive appearance at the Summer Olympics. Like on the 2016 Summer Olympics, Puerto Rico left the Olympics with a single gold medal, this time won by Jasmine Camacho-Quinn. Other athletes fell short of their Olympic medal, with Steven Piñeiro finishing sixth in the men's skateboarding street park final, and table tennis player Adriana Díaz losing a match in the third round.
Morocco competed at the 2020 Summer Olympics in Tokyo. Originally scheduled to take place during the summer of 2020, the Games were postponed to 23 July to 8 August 2021, because of the COVID-19 pandemic. The 2020 Games were the nation's fifteenth appearance at the Summer Olympics.
Paraguay competed at the 2020 Summer Olympics in Tokyo. Originally scheduled to take place from 24 July to 9 August 2020, the Games have been postponed to 23 July to 8 August 2021, because of the COVID-19 pandemic. It was the nation's thirteenth appearance at the Summer Olympics, with the exception of the 1980 Summer Olympics in Moscow because of the nation's partial support for the US-led boycott.
