How have the Scots, Irish, Welsh, Cornish, Manx and Bretons built and maintained their Celtic identities over the last three centuries? The Celtic revivals which Scotland, Ireland, Brittany and Wales started experiencing in the eighteenth century were not confined to these regions. They were supported by London and Paris, where expatriate Celts had settled. A comparison of the revivals demonstrates that the search for a distinct national voice encouraged the Welsh and Bretons, and subsequently the Scots, Irish, Manx and Cornish, to form a pan-Celtic union consolidated by three major Celtic congresses. Since the revivals, the Celtic regions have come closer together thanks to the ongoing influence of the Celtic languages, whose revitalisation has enabled the Celtic cultures to overcome attacks meant to eradicate them. Once regarded as backward and inadequate for economic prosperity, the Celtic tongues have adapted to modernity through the passage to writing and print, and through their extension to new fields. As a bridge between past and present, they form the memory of modern Celticism, annually reawakened during a festival like Pan Celtic. Comparatively, Galicia has fused memory and imagination together because this region no longer speaks any Celtic language. The Celticity Galicia began imagining in the mid-nineteenth century has given birth to Galician nationalism, embodied within an autonomous community. Similarly, the six Celtic regions have invented a Celtic ethnicity for themselves, since there is no continuity between the ancient and the modern Celts. The latter's ethnogenesis has developed into nationalisms that strengthen their distinctiveness from their dominant neighbours. Nationalism has exported Celticism beyond the geographical boundaries of the Celtic regions. The construction of Celtic Scottishness, a case study, results from a partnership between Scotland, the initiator of tartans, clan gatherings and Scottish Gaelic, and North America, which has made these aspects internationally popular. Diasporic versions of Scottish Celtic culture have been introduced into the homeland, so that original and diasporic Celtic Scottishness have blended together. The diaspora Celts give Celtic identities new forms of expression.