International Relations in the Institute of Historical Research predominantly focuses on sources relating to the major European powers and the United States over the last two hundred years, although the library does endeavour to collect, when published, sources from earlier periods. The material held by the library is of considerable breadth, and alongside the extensive runs of official diplomatic papers relating to Great Britain, France, Germany, Italy and the United States amongst others, there are journals, autobiographies and edited correspondence.
The collection (under classmark IR) has been broken up thematically and then divided either chronologically or geographically, depending on the nature of the sources. There are also accompanying materials including bibliographies and library catalogues to compliment the rest of the collection. Following this there is a classmark dedicated to international treaties followed by the main sections on diplomatic history. These have been divided into four chronological groups: pre-1870, 1870-1919, 1919-1945 and post-1945. Within these time frames are collections of diplomatic papers, autobiographies, memoirs, speeches, alongside complimentary secondary sources.