This collection explores cultural connections between and across Britain, Ireland, and Iceland from the high to late Middle Ages. The volume brings together new research from international scholars working in Celtic Studies, Norse, English, and Older Scots, exploring the ways and degrees to which insular literatures and cultures are connected with each other as well as with the wider European mainstream. Establishing the coherence of the medieval insular world as an area for literary analysis, Crossing Borders engages with a range of contemporary approaches to comparative literary and cultural studies across this region. Chapters discuss the insular histories of some of the most widely read literary works and authors of the Middle Ages, including Geoffrey of Monmouth and William Langland. They also trace the legends of Troy and of Charlemagne, as they travelled across linguistic and geographical borders. The multilingual manuscript collections of great households and families also see fresh attention; as do the political implications of language choice in a linguistically plural society. This volume reveals a complex network of literary and cultural connections, which establishes the insular world not as a periphery but as a centre.