This thesis focuses on the relationship between Gaelic Scotland and Gaelic Ireland during the classical age (c. 1200-c. 1650) - on perceptions, attitudes, and outlooks. How did the Gaels of Ireland view Scotland and the Scottish Gaels? How in turn did the Gaels? How prominent was Gaelic Scotland in the Irish Gaelic view of the world, and vice-versa? The thesis begins with an overview of intellectual paradigms that have been applied to understand the cultural position of the late medieval Gaelic world. One standard view is that Gaelic Ireland and Gaelic Scotland formed a single 'culture-province', a region of unified, largely unvarying culture. Another suggests that Gaelic Scotland was the 'poor sister', systematically dependent upon the cultural leadership and dominance of Gaelic Ireland. The thesis explores these and other related viewpoints in detail. Chapter 1 considers the historical background. Both Gaelic Ireland and Gaelic Scotland underwent significant change during this period, largely in reaction to de-Gaelicizing influences in the two countries, most notably in Scotland where the country became effectively divided into a de-Gaelicized 'Lowland' region and a Gaelic 'Highland' region. The political interactions between Gaelic Scotland and Gaelic Ireland are discussed in detail, with particular attention to the role of Scottish Gaelic mercenaries in late medieval Ireland. Chapter 2 focuses on the literary and intellectual culture of the time, exploring the ways in which the culture of Gaelic Scotland related to that of Gaelic Ireland. This culture was essentially 'pan-Gaelic', with a learned class that transcended borders. Particularly important was the role of the trained poets, who moved between the two countries. Chapter 3 is a detailed study of the vision of the relationship between Gaelic Scotland and Gaelic Ireland presented in the work of these trained poets. The worldview of the poets was a strongly Hiberocentric one, and the position of Scotland within it ambiguous and contradictory, sometimes included and sometimes overlooked.