- The International Mathematical Olympiad (IMO, since 1959)
- The International Physics Olympiad (IPhO, since 1967)
- The International Chemistry Olympiad (IChO, since 1968)
- The International Olympiad in Informatics (IOI, since 1989)
- The International Biology Olympiad (IBO, since 1990)
- The International Philosophy Olympiad (IPO, since 1993)
- The International Astronomy Olympiad (IAO, since 1996)
- The International Geography Olympiad (IGeO, since 1996)
- The International Linguistics Olympiad (IOL, since 2003)
- The International Junior Science Olympiad (IJSO, since 2004)
- The International Olympiad on Astronomy and Astrophysics (IOAA, since 2007)
- The International Earth Science Olympiad (IESO, since 2007)
The Olympiads themselves are separate competitions each with its own organizing body, even though they are loosely grouped together as "ISOs". The aims of each ISO are to promote a career in science; to challenge the brightest students from around the world; and to compare the various teaching systems of each country.
Although the competitions are aimed for secondary school pupils, the standards of the exams are extremely high. In fact, in several countries, achieving a high ranking in any ISO guarantees access to a university of choice and a fellowship.