The IISG (INternationaal Instituut voor Sociale Geschiedenis / International Institute of Social History) was founded in 1935. It is one of the world's largest documentary and research institutions in the field of social history in general and the history of the labour movement in particular. Most of the collections are open to the public.

The IISH holds over 3,000 archival collections, some 1 million printed volumes and about as many audio-visual items. The available Collections are accessible through an online catalogue, an online index of archives and inventories. The IISH is also home to a number of other documentary institutions, most notably the Netherlands Economic History Archive (NEHA) and the Press Museum. Both offer supplementary collections and services. Their material is included in the IISH catalogue. Visitors can consult the collections for reference and research in the reading room.

The IISH carries out and stimulates scholarly research. It is a respected meeting place for researchers from all over the world and organizes conferences, symposia and international research projects. The Institute publishes research results through international academic publishers and its own inhouse publishing unit. The International Review of Social History is published for the Institute by Cambridge University Press and appears three times a year, plus one supplement.