The Union of International Associations (UIA) is a non-profit non-governmental research institute and documentation center based in Brussels, Belgium, and operating under United Nations mandate. It was founded in 1907 under the name Central Office of International Associations by Henri La Fontaine, the 1913 Nobel Peace Prize laureate, and Paul Otlet, a founding father of what is now called information science.

The UIA is an independent research institute and a repository for current and historical information on the work of global civil society. It serves two main purposes: to document and promote public awareness of the work of international organizations (both INGOs and IGOs), international meetings, and world problems. The UIA also supports and facilitates the work of international associations through training and networking opportunities.

It has consultative status with ECOSOC and UNESCO.

The two founders started work setting up the Central Office of International Organisations and then conducting a survey of international organisations with headquarters in Belgium. ^[1] Then with the help of the sociologist Cyril van Overbergh they extend this research to organisations based elsewhere.^[2] After collaborating with Alfred Fried on the production of Annuaire de la Vie Internationale they produced their own edition without him.^[2]

In 1923, UIA published Code des voeux internationaux, codification générale des voeux et résolutions des organismes internationaux, with a preface by Henri La Fontaine.

• Yearbook of International Organizations
• International Congress Calendar
• Encyclopedia of World Problems and Human Potential
• UNESCO
• International Institute of Intellectual Cooperation