explores the ways Irish and Scottish literatures have influenced each other from the 1760s onwards. Although an early form of Celticism disappeared with the demise of the Celtic Revivals of Ireland and Scotland, the 'Celtic world' and the 'Celtic temperament' remained key themes in central texts of Irish and Scottish literature well into the twentieth century. Richard Barlow examines the emergence, development, and transformation of Celticism within Irish and Scottish writing and identifies key connections between modern Irish and Scottish authors and texts. By reading works from figures such as James Macpherson, Walter Scott, Sydney Owenson, Augusta Gregory, W. B. Yeats, Fiona Macleod, James Joyce, Samuel Beckett, Hugh MacDiarmid, Sorley MacLean, and Seamus Heaney in their political and cultural contexts, Barlow provides a new account of the characteristics and phases of literary Celticism within Romanticism, Modernism, and beyond.