Ships’ logbooks were kept by officers of most major national navies from as early as the mid-seventeenth century. They contain daily accounts and descriptions of the wind and weather that was encountered on voyages that became evermore wide-ranging as the European maritime empires of Britain, France, Spain and the Netherlands became established. They provide a uniquely detailed and reliable source of marine climate data from the pre-instrumental period (before the mid-nineteenth century) for many parts of the world. Several thousands of these logbooks survive in national archives and this paper reviews their contents and character and the possibilities for developing this source in climatic and historical research. The author concludes by arguing that this important and abundant source of evidence for past climates has for too long been overlooked and deserves far greater recognition than it currently enjoys.