This paper considers the evidence for the origins and development of the lake settlement tradition of Scotland and Ireland in the Late Bronze and Iron Ages. Considering a crannog 'event horizon' around the mid-first millennium BC, dating and structural evidence are compared and contrasted, and the evidence for non-domestic activity including ritual and votive deposition is contextualized. It is argued that the concurrent appearance of crannogs with the flourish of domestic monumentality in Scotland and Ireland can be seen as a consequence of the fusion of ritual and domestic spheres of life in the later first millennium BC, integrating the themes of architectural monumentality and the Iron Age reverence of water.introduction The longevity of the chronology of crannogs has been known for some time (Morrison 1982). Since the discovery of Eilean Domhnuill on North Uist it has been considered a possibility that lake settlement forms in Scotland have been in existence since the Neolithic (Armit 1996), while in Ireland the existence of related lake 'platform' structures dating to the Mesolithic has been established (O'Sullivan 1998;Fredengren 2002). However, closer analysis of the dating evidence for crannogs has indicated that the majority of sites belong to the 'Later Prehistoric' period, broadly taken to be the period 1000 BC to AD 500 (Crone 1993; Henderson 1998). The aim of this paper is to identify the evidence for the origins of lake settlement forms in Scotland and Ireland, considering the likely origin of the concept of the 'crannog', as well as the physical evidence for the structure of early lake settlements and their relationship to contemporary terrestrial settlements.The archaeology of lake settlement in the late second and early first millennium BC is better documented in Ireland than in Scotland, where so far the earliest dates for a fully developed 'crannog' structure come from Loch Tay, from the contemporary sites at Oakbank and Fearnan Hotel that may be as early as the ninth century BC (Dixon 1982). Lake settlement in the Later Bronze Age is well represented in Ireland, and several large-scale excavations have meant that the nature of this early horizon of lake and wetland habitation is relatively well documented. Besides a range of sites which have been demonstrated to have been constructed, inhabited and abandoned in the Later Bronze Age (e.g. Cullyhanna, Hodges 1958; Lough Eskragh, Collins and OXFORD JOURNAL OF ARCHAEOLOGY 25(4) 389-412 2006