Prehistoric Orkney refers to a period in the human occupation of the Orkney archipelago of Scotland that was the latter part of these islands' prehistory. The period of prehistory prior to occupation by the genus Homo is part of the geology of Scotland. Although some written records refer to Orkney during the Roman invasions of Scotland, prehistory in northern Scotland does not end until the commencement of the Early Historic Period around AD 600.
There are numerous important prehistoric remains in Orkney, especially from the Neolithic period, four of which form a World Heritage Site. There are diverse reasons for the abundance of the archaeological record. The sandstone bedrock provides easily workable stone materials and the wind-blown sands have helped preserve several sites. The relative lack of industrialisation and low incidence of ploughing also have helped to preserve these ancient monuments. Local tradition hints at both a fear and veneration of these ancient structures (perhaps inherited from the Norse period of occupation) that may have helped to retain their structural integrity.