This article approaches the material culture of late medieval Gaelic Ireland as an active locus for the negotiation and display of group identities. It works against assumptions about the failures of material and book culture to present, adequately, evidence of ethnic identity in the Middle Ages. Instead, it uses Florin Curta’s productive, valuable theories about ethnic markers in the archaeological record to analyze material objects, specifically the Book of Ballymote and various refurbished book shrines, for evidence of ethnic identity markers, generated by the external pressures of shifting power relations. Thematically, these objects are linked by deliberate associations with a perceived ancestral past, with the ultimate purpose of asserting claims over territory in times of dispute and change. This article argues that markers of group identity, and therefore ethnicity, are discernible in the contents and purposes of these objects, when analyzed in their appropriate historical contexts. The analysis of these objects is therefore a productive method of thinking about the function of ethnicity in late medieval Gaelic Ireland, with possible implications for other groups and periods across the Middle Ages.