The Historical Archives of the European Union (HAEU), located in Florence (Italy), is the official archives for the historical documents of the Institutions of the European Union. It is also a research centre dedicated to the archival preservation and study of European integration and is part of the European University Institute (EUI).

The Historical Archives of the European Union was established in 1983 following the regulation by the Council of the European Communities and the decision by the Commission of the European Communities to open their historical archives to the public. A subsequent agreement in 1984 between the Commission of the European Communities and the EUI laid the groundwork for establishing the Archives in Florence, and the HAEU opened its doors to researchers and the public in 1986. In 2011 a Framework Partnership Agreement between the EUI and the European Commission reinforced the Historical Archives’ role in preserving and providing access to the archival holdings of the European Union's institutions and regulated the acquisition and treatment of private archives. In March 2015 the Council of the European Union amended the decisions of 1983 with the Council Regulation (EU) 2015/496.

The HAEU preserves and makes accessible the archival holdings of EU Institutions and Agencies according to the 30-year rule governing access to archives of the European Union. It also collects and preserves private papers of individuals, movements and international organizations involved in the European integration process. It facilitates research on the history of the European Union and its predecessor institutions, promotes public interest in European integration and enhances transparency in the functioning of European Union Institutions.

The holdings are composed of funds coming from the European Institutions, their predecessor institutions and European Union Agencies.

Among its holdings are the archives of the European Coal and Steel Community (ECSC), the European Economic Community (EEC), the European Atomic Energy Community (Euratom), the Common Assembly of the ECSC, the European Parliamentary Assembly, the Court of Justice of the European Union, the Economic and Social Committee, the Court of Auditors, and the European Investment Bank.

It also holds private deposits and collections from individuals, organisations and associations that advocated, supported and implemented the Post-World War II European conciliation and integration process. These holdings include the archival papers of the European Space Agency (ESA), the Assembly of Western European Union (WEU), the European Council for Municipalities and Regions (CCRN), the European League for Economic Cooperation (LECE) and a unique collection of federalist archives, for example the European Movement (ME), the Union of European Federalists (UEF) and the 'Centre international de formation européenne (CIFE)'.

In the framework of the activities of the ‘EU Inter-institutional Web Preservation Working Group’ and in collaboration with the Internet Memory Foundation the HAEU launched in 2013 an archiving pilot project on EU institutions’ websites. These websites are captured quarterly since the end of 2013 and made available on the HAEU’s home page.

Since 2012, the HAEU has his seat at the historic 'Villa Salviati' in Florence.