The first of the International Mathematical Olympiads (IMOs) was held in Romania in 1959. The oldest of the International Science Olympiads, the IMO has since been held annually, except in 1980. That year, the competition initially planned to be held in Mongolia was cancelled due to the Soviet invasion of Afghanistan. Because the competition was initially founded for Eastern European countries participating in the Warsaw Pact, under the influence of the Eastern Bloc,[1] the earlier IMOs were hosted only in Eastern European countries, gradually spreading to other nations.[2]
The first IMO was held in Romania in 1959. Seven countries entered - Bulgaria, Czechoslovakia, East Germany, Hungary, Poland, Romania and the Soviet Union - with the hosts finishing as the top-ranked nation.[3] The number of participating countries has since risen: 14 countries took part in 1969, 50 in 1989, and 104 in 2009.[4]
North Korea is the only country whose entire team has been caught cheating, resulting in its disqualification at the 32nd IMO in 1991 and the 51st IMO in 2010.[5] (However, the 2010 case was controversial.[6] [7]) There have been other disqualifications of contestants due to cheating, but such cases are not officially made public.[8] In January 2011, Google gave €1 million to the IMO organization to help cover the costs of the events from 2011 to 2015.[9]
| scope=col | scope=col | Venue | scope=col | Year | Date | scope=col | Top-ranked country[10] | References | |
|---|---|---|---|---|---|---|---|---|---|
| 1 | scope=row |  Brașov and Bucharest | 1959 | June 23 - July 31 | Romania | [11] | |||
| 2 | scope=row | Sinaia | 1960 | July 18 - July 25 | |||||
| 3 | scope=row |  Veszprém | 1961 | July 6 - July 16 | Hungary | ||||
| 4 | scope=row | 1962 | July 7 – July 15 | Hungary | |||||
| 5 | scope=row |  Warsaw and Wrocław | 1963 | July 5 – July 13 | |||||
| 6 | scope=row | Moscow | 1964 | June 30 - July 10 | |||||
| 7 | scope=row | East Berlin | 1965 | June 13 - July 13 | |||||
| 8 | scope=row |  Sofia | 1966 | July 3 - July 13 | |||||
| 9 | scope=row | Cetinje | 1967 | July 7 - July 13 | |||||
| 10 | scope=row | Moscow | 1968 | July 5 - July 18 | |||||
| 11 | scope=row | Bucharest | 1969 | July 5 - July 20 | Hungary | ||||
| 12 | scope=row | Keszthely | 1970 | July 8 - July 22 | Hungary | ||||
| 13 | scope=row | Žilina | 1971 | July 10 - July 21 | Hungary | ||||
| 14 | scope=row | Toruń | 1972 | July 5 - July 17 | |||||
| 15 | scope=row | Moscow | 1973 | July 5 - July 16 | |||||
| 16 | scope=row | Erfurt and East Berlin | 1974 | July 4 - July 17 | |||||
| 17 | scope=row | Burgas and Sofia | 1975 | July 3 - July 16 | Hungary | ||||
| 18 | scope=row |  Lienz | 1976 | July 2 - July 21 | |||||
| 19 | scope=row | Belgrade | 1977 | July 1 - July 13 |  United States | ||||
| 20 | scope=row | Bucharest | 1978 | July 3 - July 10 | Romania | ||||
| 21 | scope=row |  London | 1979 | June 30 - July 9 | |||||
| - | scope=row colspan=5 | [12] | |||||||
| 22 | scope=row | Washington, D.C. | 1981 | July 8 - July 20 | United States | align=center | |||
| 23 | scope=row | Budapest | 1982 | July 5 - July 14 | |||||
| 24 | scope=row |  Paris | 1983 | July 3 - July 12 | |||||
| 25 | scope=row | Prague | 1984 | June 29 - July 10 | |||||
| 26 | scope=row |  Joutsa | 1985 | June 29 - July 11 | Romania | ||||
| 27 | scope=row | Warsaw | 1986 | July 4 - July 15 | United States | ||||
| 28 | scope=row |  Havana | 1987 | July 5 - July 16 | Romania | ||||
| 29 | scope=row |  Sydney and Canberra | 1988 | July 9 - July 21 | |||||
| 30 | scope=row | Braunschweig | 1989 | July 13 - July 24 |  China | ||||
| 31 | scope=row | Beijing | 1990 | July 8 - July 19 | China | ||||
| 32 | scope=row |  Sigtuna | 1991 | July 12 - July 23 | |||||
| 33 | scope=row | Moscow | 1992 | July 10 - July 21 | China | ||||
| 34 | scope=row |  Istanbul | 1993 | July 13 - July 24 | China | ||||
| 35 | scope=row |  Hong Kong[13] | 1994 | July 8 - July 20 | United States | ||||
| 36 | scope=row |  Toronto | 1995 | July 13 - July 25 | China | [14] | |||
| 37 | scope=row |  Mumbai | 1996 | July 5 - July 17 | Romania | [15] | |||
| 38 | scope=row |  Mar del Plata | 1997 | July 18 - July 31 | China | [16] | |||
| 39 | scope=row | Taipei | 1998 | July 10 - July 21 | [17] | ||||
| 40 | scope=row | Bucharest | 1999 | July 10 - July 22 | China | [18] | |||
| 41 | scope=row | Daejeon | 2000 | July 13 - July 25 | China | [19] | |||
| 42 | scope=row | Washington, D.C. | 2001 | July 1 - July 14 | China | [20] | |||
| 43 | scope=row | Glasgow | 2002 | July 19 - July 30 | China | [21] | |||
| 44 | scope=row |  Tokyo | 2003 | July 7 - July 19 | Bulgaria | [22] | |||
| 45 | scope=row |  Athens | 2004 | July 6 - July 18 | China | [23] | |||
| 46 | scope=row |  Mérida | 2005 | July 8 - July 19 | China | [24] | |||
| 47 | scope=row |  Ljubljana | 2006 | July 6 - July 18 | China | [25] | |||
| 48 | scope=row | Hanoi | 2007 | July 19 - July 31 | [26] | ||||
| 49 | scope=row |  Madrid | 2008 | July 10 - July 22 | China | [27] | |||
| 50 | scope=row |  Bremen | 2009 | July 10 - July 22 | China | [28] | |||
| 51 | scope=row |  Astana | 2010 | July 2 - July 14 | China | [29] | |||
| 52 | scope=row |  Amsterdam | 2011 | July 13 - July 24 | China | [30] | |||
| 53 | scope=row | Mar del Plata | 2012 | July 4 - July 16 | [31] | ||||
| 54 | scope=row | 2013 | July 18 - July 28 | China | [32] | ||||
| 55 | scope=row | Cape Town | 2014 | July 3 - July 13 | China | [33] | |||
| 56 | scope=row |  Chiang Mai | 2015 | July 4 - July 16 | United States | [34] | |||
| 57 | scope=row | Hong Kong | 2016 | July 6 - July 16 | United States | [35] | |||
| 58 | scope=row | 2017 | July 12 - July 23 | [36] | |||||
| 59 | scope=row | Cluj-Napoca | 2018 | July 3 - July 14 | United States | [37] | |||
| 60 | scope=row | Bath | 2019 | July 11 - July 22 | China United States | [38] | |||
| 61 | scope=row |  St. Petersburg (online) | 2020 | September 19 - September 28 | China | [39] [40] | |||
| 62 | St. Petersburg (online) | 2021 | July 14 - July 24 | China | [41] | ||||
| 63 | scope=row |  Oslo (hybrid) | 2022 | July 6 – July 16 | China | [42] | |||
| 64 | scope=row | Chiba | 2023 | July 2 – July 13 | China | [43] | |||
| 65 | scope=row | Bath | 2024 | July 11 – July 22 | United States | [44] | |||
| 66 | scope=row | Sunshine Coast | 2025 | July 10 – July 20 | TBD | [45] | |||
| 67 | scope=row | Shanghai | 2026 | TBD | TBD | [46] | |||
| 68 | scope=row | (TBA) | 2027 | TBD | TBD | [47] | |||