Northumbria was the most northerly Anglo-Saxon kingdom; its impressive landscape featured two sweeping coastlines, which opened the area to a variety of cultural connections. This book explores influences that emanated from the Gaelic-speaking world, including Ireland, the Isle of Man, Argyll and the kingdom of Alba (the nascent Scottish kingdom). It encompasses Northumbria's Golden Age, the political and scholarly high-point of the seventh and early eighth centuries, and culminates with the kingdom's decline and fragmentation in the Viking Age, which opened up new links with Gaelic-Scandinavian communities. Political and ecclesiastical connections are discussed in detail; the study also covers linguistic contact, material culture and the practicalities of travel, bringing out the realities of contemporary life. This interdisciplinary approach sheds new light on the west and north of the Northumbrian kingdom, the areas linked most closely with the Gaelic world. Overall, the book reveals the extent to which Gaelic influence was multi-faceted, complex and enduring.