In this paper we present a three-stranded investigation of all ‘archaeological islands’ (including crannogs) across Scotland, with a particular focus on the Outer Hebrides. The first strand is a synthesis and critical review of the archaeological record relating to 582 ‘archaeological island’ sites. This research enabled us to characterise the nature of any previous work (including dating evidence) undertaken on each, and thus to establish the first ever open access, holistic, accurate dataset of these sites. The second strand is new underwater survey carried out at 30 archaeological islands across the southern Outer Hebrides. This enabled us to acquire further information about and dating evidence for these sites; notably, this included new evidence for Neolithic occupation on three, increasing the total of known Neolithic islets in the region to 11. The third strand involved a thorough re-assessment of a wide body of archaeological literature relating to early excavations and finds. This research identified potential Neolithic material culture on a further 15 archaeological islands across the rest of Scotland. We conclude by discussing the potentially very significant implications of this early material, considering the possibility that crannogs could have been constructed in the Neolithic beyond the Outer Hebrides.