The Islamic manuscript collection has been acquired by Cambridge University Library from many sources over the period of the past four centuries. Most of these have been acquired from private donations and were originally closely allied with the start of Arabic teaching in the early seventeenth century. Many other collections followed and a chronology of significant donations is described with details of each donor and something of the contents of each collection. Major collections such as those of Erpenius, George Lewis, J.L. Burckhardt, E.H. Palmer and E.G. Browne are dealt with in more detail. Some important individual manuscripts are also described and examples are given of manuscripts with interesting codicology or illumination. A description of the collection’s management within the Library and a history of its cataloguing is also given.