ESO, the European Organisation for Astronomical Research in the Southern Hemisphere, is an inter-governmental organisation with 15 Member States.

The Organisation is led by the Director General who is appointed by the ESO Council. The current Director-General is Prof. Tim de Zeeuw.

The main organisational and managerial units of ESO are the Directorates and Divisions. The Directorates are: Directorate of Programmes, Directorate of Operations, Directorate for Science, and Directorate of Engineering. The Divisions are: Telescope, Instrumentation, Technology, La Silla Paranal Observatory, ALMA Construction, European ALMA Support Centre, Data Management and Operations, Software Development, Administration, and Human Resources. Most of the divisions are located within a Directorate. Divisions are organised in Departments, some of which consist of two or more Groups.

For an overview of ESO's organisational structure, please consult the organigram of ESO (PDF) (as of 1 March 2013).