The International Astronomical Union (IAU; French: Union astronomique internationale, UAI) is an international non-governmental organization (INGO) with the objective of advancing astronomy in all aspects, including promoting astronomical research, outreach, education, and development through global cooperation.

Individual members are organised into divisions, committees, and working groups centered on particular subdisciplines, subjects, or initiatives.

It sponsors nine annual symposia and holds a triannual General Assembly that sets policy and includes various scientific meetings.

[6] Among other activities, it acts as the recognized authority for assigning designations and names to celestial bodies (stars, planets, asteroids, etc.)

The Minor Planet Center also operates under the IAU, and is a "clearinghouse" for all non-planetary or non-moon bodies in the Solar System.

[10] Thirty-two Commissions (referred to initially as Standing Committees) were appointed at the Brussels meeting and focused on topics ranging from relativity to minor planets.

By the end of the first General Assembly, ten additional nations (Australia, Brazil, Czechoslovakia, Denmark, the Netherlands, Norway, Poland, Romania, South Africa, and Spain) had joined the Union, bringing the total membership to 19 countries.

Twelve of the fourteen past General Secretaries in the period 1964–2006 contributed their recollections of the Union's history in IAU Information Bulletin No.

[14][15] Starting in 2024, the Union, in partnership with the United Nations, is poised to play a critical role in developing the legislation and framework for lunar industrialization.

[3] Membership also includes 82 national members, professional astronomical communities representing their country's affiliation with the IAU.

The Assembly determines IAU policy, approves the Statutes and By-Laws of the Union (and amendments proposed thereto) and elects various committees.

GTTP is also concerned with the effective use and transfer of astronomy education tools and resources into classroom science curricula.