Although Richard II's Irish expedition of 1394–95 has attracted considerable scholarly attention, the focus has largely been on Richard's relations with the colonial administration in Ireland, pointing mainly to the colonial government's plea for greater royal investment in the colony as the main factor underpinning Richard's decision to intervene in Ireland. Little attention, by comparison, has been devoted to exploring the king's relations with both the Gaelic Irish and Gaelic Scottish nobility. Using Richard's relations with the expanding Gaelic world as the main case study, this article reconsiders how developments in the Gaelic west influenced the king's decision to intervene in Ireland. Set against the backdrop of Anglo-Scottish relations and the Hundred Years’ War, the article draws on a broad range of Gaelic sources from Ireland and Scotland, English and Scottish governmental records, and material from the Avignon papacy. It uncovers and traces the development of the main Gaelic Irish and Gaelic Scottish dynasties during the late fourteenth century, their relationships with one another, and their unfolding connections with the English and Scottish crowns. By locating Richard's expeditions within the broader archipelagic context, this article argues that the wider Gaelic world, though on the geographic periphery of Ireland and Scotland, was capable of exerting a far greater degree of influence on the course of “British” politics than has previously been acknowledged.