The Olympic Games are traditionally said to have first been held in Ancient Greece in 776 BC. They were held in the city of Olympia in honour of the Greek god Zeus, and were a series of athletic competitions between the various Greek city states, with the winner of each event receiving an olive leaf wreath or crown. Some of the traditions of the modern games date back to the ancient games; like the modern games, the ancient games were held every four years, and the symbolism of peace in the modern games was inspired by ancient games, as a truce would be enacted between all the Greek city states during the games to allow athletes to travel safely between their homes and Olympia. Unlike the modern games, the ancient games were only open to Greek men who were free (not slaves), and anyone who wished to participate had to prove Greek ancestry. Women were not allowed to participate, and married women were not even allowed to attend as spectators, though women who owned horses could enter them in the equestrian events (albeit ridden by male jockeys), and would also be declared Olympic champions should their horses win events. The Olympic Games would continue to be held even after Greece came under Roman rule, but would eventually be banned by Emperor Theodosius I in AD 393 after he declared Christianity the state religion of Rome and mandatory for all Roman subjects, as he viewed the games as a Pagan tradition that undermined Christianity.
The first talks of reviving the games began in 1821, after Greece gained independence from the Ottoman Empire. A donation from Evangelos Zappas, a wealthy Greek-Romanian philanthropist led to games being held in Athens in 1859, 1870 and 1875, with athletes coming from Greece and the Ottoman Empire. Meanwhile, a British educationalist known as William Penny Brooks would start an Olympian Class in 1850, which were and continue to be held every year at Much Wenlock, England. Inspired by both these events, French baron Pierre de Coubertin would go on to found the International Olympic Committee (IOC) in 1890. Under the auspices of the IOC, the first modern Olympic Games would be held in Athens in 1896, with the Panathinaiko Stadium, which had been renovated for the games in 1870, serving as the main stadium for the games. The first games in 1896 would also be a male-only event, with women only allowed to compete starting from the 1900 edition in Paris.
For much of its history, the modern Olympics required all participants to be amateurs, or in other words to never have received any monetary compensation whatsoever for sports-related activities; a rule inspired by the ideals of the traditional English gentleman in the 19th century. However, with the start of the Cold War, the Soviet Union and its communist allies would get around this rule by nominally hiring their athletes in other occupations, but in practice allowing them to be on perpetual paid leave to train full-time. As a result, the rules on amateurism were gradually relaxed, and were eventually completely abolished in 1992, though the sports of boxing and wrestling continue to use amateur rather than professional fight rules. Another vestige of the amateurism rule can be seen in men's association football (soccer), where participants are required to be aged 23 or younger (except for three over-age players allowed per team) — in part because FIFA does not want to "devalue" their World Cup and European Championships.
In the early years, Summer Olympics were often held over a course of several months and competitors were not clearly separate from the general population, meaning pretty much anybody could show up and participate. Similarly, venues were rarely purpose built and permanent. Several of the pre World War I games were held together with a World Exhibition and several of the Olympic traditions actually date back to "Intercalated Games" that were to be held between two regular games and always in Athens but abandoned after only one such event was held.
The United States leads the all-time medal count in the Summer Olympics, having won over 1,000 gold medals, with the Soviet Union in a distant second clocking in at just under 400. However, third place Great Britain is the only team to have won gold at every edition of the Summer Olympics, due to the fact that the Americans boycotted the 1980 games in Moscow.
Since the 1988 Summer Games, all Olympic Games have been followed immediately by the Paralympic Games for disability sports in the same city and using most if not all of the same venues. Joint hosting of the Olympics and Paralympics (both Summer and Winter) has been official policy since 2001.
- Amsterdam – hosted in 1928; had previously hosted some sailing events at the 1920 Games.
- Antwerp – hosted in 1920.
- Athens - hosted the first modern Olympic Games in 1896 and again hosted them in 2004, plus the only Intercalated Games in 1906; surprisingly little remains even from the 2004 Games. However, the main stadium of the 1896 games, the Panathinaiko Stadium, which hosted the archery events and the finish of the marathon in 2004, still stands and is a major historical landmark and tourist attraction.
- Atlanta - hosted in 1996. Most of the infrastructure still stands, but the main stadium was reconfigured for baseball immediately after the Games and has been reconfigured again for American football.
- Barcelona – hosted in 1992. Most of the Olympic infrastructure still stands.
- Beijing – hosted in 2008, which is the most expensive summer games to date, and will become the first city to have hosted both the Summer and Winter Games in 2022.
- Berlin - planned host for the 1916 games which were cancelled due to World War I; ultimately hosted the 1936 games awarded before Hitler took over. Olympiastadion redesigned but still extant. Some other venues still extant in some form but hard to see for the casual observer. The S-Bahn which had been developed for decades before in part got upgrades for the games.
- Helsinki – scheduled to host the games in 1940 (after Tokyo gave them back to the IOC due to the Pacific War); due to World War II, they were postponed until 1952. The Olympic stadium has been the most important outdoor sports venue in Helsinki ever since, but is closed for a major renovation until 2019.
- London – the first city to host three Olympics (1908, 1948, 2012), with most of the 2012 infrastructure still present. The exact marathon distance of 42,195 m (138,435 ft) was set for the 1908 games to have the final stretch before the monarch. Planned host for the 1944 games which were cancelled due to World War II, but would eventually host 4 years later after the end of the war.
- Los Angeles – hosted 1932 and 1984 Olympics, the latter with a large Soviet-led boycott, and will host in 2028. The main stadium in 1932 and 1984, the Los Angeles Memorial Coliseum, is still in active use and is planned to be used in 2028 as well. Some of the other 1932 infrastructure and much more of the 1984 infrastructure still stands.
- Melbourne – hosted in 1956 with the exception of equestrian events, which were held in Stockholm due to Australian quarantine laws. The main stadium, the Melbourne Cricket Ground, is still in active use; it is mostly outwardly unchanged from its Olympic configuration, although significantly modernised within.
- Mexico City - hosted the 1968 games where many records were broken due to high altitude, but several political controversies overshadowed the events.
- Montreal - bankrupted itself with the 1976 games that cost more than expected, especially the Olympic Stadium that proved a less than inspired design and would struggle for years to find a suitable tenant.
- Moscow - hosted in 1980 with a large US-led boycott. The main stadium was renovated for the 2018 FIFA World Cup.
- Munich - host of the 1972 Olympics, which was overshadowed by a terrorist attack that led to the deaths of 11 Israeli team members. Much of the Olympic infrastructure (including Olympiastadion) still exists. The U-Bahn (Germany's third) opened a year ahead of the game and was partly built for the games
- Paris – hosted 1900 and 1924 Olympics, and will host in 2024. The main stadium from 1924, located in the suburb of Colombes, still stands and will be used for field hockey in 2024, but has been heavily downsized from its 1924 configuration. The 1900 games was the first that women were allowed to participate.
- Rio de Janeiro - hosted in 2016 after Brazil had already hosted the 2014 FIFA World Cup; many venues are already beyond use or were never planned to be permanent.
- Rome - hosted in 1960; the first city of one of the major Axis Powers of World War II to host after the war. The main stadium is still in use, though it was extensively renovated for the 1990 FIFA World Cup.
- Seoul - hosted in 1988 after an attempt to jointly host with sites in North Korea fell through. Most of the Olympic infrastructure still stands.
- St. Louis - hosted in 1904. The main stadium, located just outside the city limits, still exists on the campus of Washington University, but has been heavily renovated.
- Stockholm – hosted in 1912, and also hosted equestrian events in 1956.
- Sydney - hosted in 2000. Most of the Olympic infrastructure still stands.
- Tokyo – the next Summer Olympics host in 2020; also hosted in 1964, with the first Shinkansen running just in time for the 1964 Games. Planned host for the 1940 games, which were eventually cancelled due to the outbreak of World War II.
First held in 1924, the Winter Olympics were originally held in the same year as Summer Olympics and often in the same country. With the increasing size of the Olympic Games and the increasing financial commitment for hosts, it was decided to split Summer and Winter Games up, and the Winter Olympics were scheduled to be in the year of the Soccer World Cup to avoid the two biggest worldwide sports events going head to head.
Norway leads the all-time Winter Olympics medal table, with the United States in second place, though the United States is the only country to have won gold at every edition of the Winter Olympics.
Similarly to the Summer Games, each Winter Olympics since 1992 has been immediately followed by the Winter Paralympics, also in the same host city and using the same venues.
- Albertville – hosted in 1992. Most of the infrastructure still stands, though some of it has been renovated. The stadium used for the opening and closing ceremonies was intended to be temporary and was removed immediately after the Olympics, with parts of it used in that year's Summer Games in Barcelona. A monument stands on the site today.
- Beijing – scheduled to host in 2022, which will make it the first city to have hosted both the summer and winter games.
- Calgary – hosted in 1988, with almost all of the Olympic infrastructure (much of which is in surrounding areas) still present.
- Chamonix - hosted the very first Winter Olympics in 1924.
- Cortina d'Ampezzo – hosted in 1956, after having been named as the host of the 1944 Games that had been scrapped due to World War II. Scheduled to co-host in 2026 along with Milan.
- Garmisch-Partenkirchen – hosted in 1936; less overtly Nazified than that year's Summer Games in Berlin.
- Grenoble – hosted in 1968.
- Innsbruck – hosted in 1964 and 1976, the latter time on short notice after voters in Denver turned down hosting duties.
- Lake Placid – hosted in 1932 and 1980. The 1980 Games used much of the 1932 infrastructure. Most of the venues still exist; the most notable exception is that the 1980 luge track was demolished and replaced with a new track for all sliding sports (bobsled, luge, skeleton). The site of the 1980 "Miracle on Ice", in which the US men's hockey team defeated the heavily favored Soviets, has since been renamed after the 1980 team's head coach Herb Brooks.
- Lillehammer – hosted in 1994.
- Milan – scheduled to co-host in 2026 alongside Cortina.
- Nagano – hosted in 1998.
- Oslo – hosted in 1952.
- Pyeongchang – hosted in 2018.
- Salt Lake City – hosted in 2002, with almost all of the Olympic infrastructure (much of which is in outlying areas) still present. The area's current light rail system was started as transportation for the Games.
- Sapporo – hosted the first Winter Games in Asia in 1972. It had been named as the 1940 host, but World War II scuttled that plan.
- Sarajevo – hosted in 1984. Most of the infrastructure was damaged or destroyed during the Bosnian War of the 1990s. The city's main indoor arena was built on the foundation of the 1984 indoor arena that had been destroyed in the war.
- Sochi - hosted in 2014; the most expensive games to date.
- Squaw Valley – hosted in 1960.
- St. Moritz – hosted in 1928 and 1948.
- Turin – hosted in 2006.
- Vancouver – hosted in 2010. Almost all of the infrastructure, both in Vancouver and in the Whistler resort area, still stands. However, the main stadium, BC Place, which had an air-supported roof in 2010, now has a cable-supported retractable roof.
Accessibility of tickets varies greatly. Opening and closing ceremonies, as well as finals, are very desired, while tickets to minor events can in some cases be obtained at entrance. The ability to acquire tickets also depends on the host. While tickets for Handball events were easy to get in Rio, they'll likely be much more in demand in Paris.
Availability of travel accommodation has varied a lot between games. As a general rule: The smaller the city, the bigger the price-gouging.
There are some museums and training facilities related to the Olympics open for tour year round.
Besides the Olympic Games, there are also other multi-sport events that are organised loosely based on the format of the Olympics, albeit on a smaller scale. These typically only feature countries in specific regions, or in specific international groupings, and often feature non-Olympic sports that are popular among the participating nations.
- The Paralympic Games for disability sports, with both summer and winter versions. All Olympic bids are required to include the Paralympics, and the successful bidder will host both events in the same year, with the Paralympics held shortly after the Olympics. As such, the next Summer Paralympics will be hosted by Tokyo in 2020, and the next Winter Paralympics by Beijing in 2022.
- The World Games, for sports, or disciplines within a sport, that are not contested in the Olympics. Held in the year after the Summer Olympics. The next World Games will be hosted by Birmingham, Alabama in 2021.
- The Asian Games among the countries of Asia; the second largest multi-sports games after the Summer Olympics. Held in the same year as the Winter Olympics. The next edition will be in Hangzhou, China in 2022.
- The Winter Asian Games, operated by the same body but featuring only winter sports. Held in the year before the Winter Olympics. The next edition will be in 2021, but no location has yet been announced.
- The Commonwealth Games among the countries of the Commonwealth of Nations; the third largest multi-sports games. Unlike other multi-sport events, para-sports events are held as part of the main games with the able-bodied sports events. Held in the same years as the Winter Olympics. The next edition will be in 2022 in Birmingham, England.
- The Pan American Games among the countries of The Americas. Held in the year before the Summer Olympics. The 2019 edition just finished in Lima, Peru; the next edition will be in 2023 in Santiago, Chile.
- Jeux de la Francophonie among the countries of La Francophonie. The Canadian provinces of Quebec and New Brunswick send separate teams from the Canadian team, and the Belgian team is restricted to sending Francophone athletes. Held in the year after the Summer Olympics. The next edition is scheduled in 2021.
- The African Games among the countries of Africa. Held in the year before the Summer Olympics. The next edition will be in 2019 in Casablanca, Morocco.
- The Lusophony Games among the world's Portuguese-speaking countries.
- The Pacific Games among the countries of Oceania except Australia and New Zealand. Held in the year before the Summer Olympics. The next edition will be in 2019 in Apia, Samoa.
- The Southeast Asian Games (SEA Games) among the countries of Southeast Asia. The next edition will be held in Manila, Philippines in 2019.
- The Central American Games, held in the year after the summer Olympics only involving Central America.
- The Central America and Caribbean Games - held in the year of winter Olympics dating to the 1920s; the second oldest international multi-sport games.