The construction of collective identities is closely linked to the process described as ‘creation or invention of tradition’. Memories of the past define the present, but these memories are subject to continuous redefinitions and refinements that allow them to be adapted to the circumstances of each historical period. Based on these general considerations, the present paper aims to explore the various and sometimes even contradictory uses of the concept ‘Celtic’ based on two specific case-studies from the Atlantic area. Firstly, the north of the Iberian Peninsula and in particular the region of Galicia, which is conceived in Spain as the embodiment of everything ‘Celtic’, from music to landscapes and traditional festivities. And secondly, Wales, where the concept of Celticity and the use of the Welsh language plays a major role for peoples’ identities. Both examples constitute an excellent framework to analyse the dialectics between scientific discourse and popular culture.