This short study of the history of the Order of St John of Jerusalem, Rhodes and Malta, also known as the Knights Hospitaller, is intended as an introduction to the Order for academics working in other fields, as well as the interested general reader. Beginning with a consideration of the origins of the Order as a hospice for pilgrims in Jerusalem in the eleventh century, it traces the Hospitaller's development into a military order during the first part of the twelfth century, and its military activities on the frontiers of Christendom in the eastern Mediterranean, Spain and eastern Europe during the middle ages and into early modern period: its role in crusades and in wars against non-Christians on land and at sea, as well as its role in building and maintaining fortresses. It also considers the Order's activities away from the frontiers of Christendom: its economic activities and its relations with patrons and rulers throughout Europe, as well as its hospitaller work and its religious life. The focus of the study is on the medieval period down to the loss of Rhodes in 1522, but the final chapters of the book consider the Order's history on Malta from the sixteenth to the end of the eighteenth century, and from the loss of Malta in 1798 to the present day. HELEN NICHOLSON is Senior Lecturer in History, Cardiff University.