List of International Mathematical Olympiads

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, the earlier IMOs were hosted only in Eastern European countries, gradually spreading to other nations.

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. The number of participating countries has since risen: 14 countries took part in 1969, 50 in 1989, and 104 in 2009.

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. (However, the 2010 case was controversial. ) There have been other disqualifications of contestants due to cheating, but such cases are not officially made public. In January 2011, Google gave €1 million to the IMO organization to help cover the costs of the events from 2011 to 2015.