The International Science Olympiads are a group of worldwide annual competitions in various areas of science. The competitions are designed for the 4-6 best high school students from each participating country selected through internal National Science Olympiads, with the exception of the International linguistic olympiad (IOL), which allows two teams per country, the International olympiad in informatics (IOI), which allows two teams from the hosting country, and the International junior sciencs olympiad (IJSO), which is designed for junior secondary students. To date there are 12 such ISOs:

•     The International Mathematical Olympiad (IMO, since 1959; not held in 1980)
•     The International Physics Olympiad (IPhO, since 1967; not held in 1973, 1978, 1980)
•      The International Chemistry Olympiad (IChO, since 1968; not held in 1971)
•      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)