A highly dynamic fluvial environment acted upon by a complex human society capable of landscape-changing hydro-engineering works, the Nile of Egypt has undergone significant and constant change during the period of human inhabitation of its basin. This thesis looks at navigation on the Nile network in the period from Islamic conquest of Egypt in the mid- seventh century AD to the 15th century AD. The mostly Arabic historical and geographical texts of that period describe a waterway network that differs markedly from that described by the authors of antiquity, and from that seen today. This thesis investigates these texts, in concert with geological, archaeological and cartographic data, and charts the routes of the major medieval waterways of Egypt within the modern landscape in Cartesian spatial terms. The chronology of major changes in the network - the comings and goings of artificial and natural waterways - is also established. Having proposed routes and chronologies for the major medieval Nile waterways, the thesis then investigates the sailing conditions encountered on the river network, including the hydrological cycles and meteorological conditions effecting navigation, the obstacles and hazards encountered en route, and the times taken to make long-distance journeys. It also looks at the interface between Nile navigation and that of the adjacent Mediterranean and Red Seas. Finally, the thesis considers the location of the major ports of the Nile Delta and the Red Sea, and considers the factors - navigational and otherwise - determining the choice of harbour site. It concludes that, far from being exclusively the product of a process of navigational optimalisation, the siting of these ports was the outcome of a far more complex set of prerogatives, among which navigational ease was one factor to be considered among many.