The International Science Olympiads are a group of worldwide annual competitions in various areas of the formal sciences, natural sciences, and social sciences. 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 IOL, which allows two teams per country, the IOI, which allows two teams from the hosting country, and the IJSO, which is designed for junior secondary students. Early editions of the first Olympiads were limited to the Eastern Bloc, but later they gradually spread to other countries.

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.

Science Olympiads are international student competitions. There are 12 commonly recognized International Science Olympiads:

#	Science	Symbol	Year	Host Country (For 2023)	Host Country (For 2024)
1	International Mathematical Olympiad	IMO	since 1959	Japan	United Kingdom
2	International Physics Olympiad	IPhO	since 1967	Japan	Iran
3	International Chemistry Olympiad	IChO	since 1968	Switzerland	Saudi Arabia
4	International Olympiad in Informatics	IOI	since 1989	Hungary	Egypt
5	International Biology Olympiad	IBO	since 1990	UAE	Kazakhstan
6	International Philosophy Olympiad	IPO	since 1993	Greece	Finland
7	International Astronomy Olympiad	IAO	since 1996	China
8	International Geography Olympiad	iGeo	since 1996	Indonesia	Ireland
9	International Linguistics Olympiad	IOL	since 2003	Bulgaria	Brazil
10	International Junior Science Olympiad	IJSO	since 2004	Thailand	Romania
11	International Earth Science Olympiad	IESO	since 2007	Online	China
12	International Olympiad on Astronomy and Astrophysics	IOAA	since 2007	Poland	Brazil

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