The question of authenticity in language has been approached from a number of theoretical standpoints. A significant type of feature which may bestow authenticity and legitimacy is the linguistic. Linguistic performance can be viewed in terms of either the unreflectingly fluent and competent use by the ideal native speaker or, in opposition, the inauthenticity of the non-native language learner. As pointed out by Martin Gill in his paper “Exclusive Boundaries, Contested Claims: Authenticity, Language and Ideology”, authentic speech is romanticised as “native, spoken, verbatim, unrehearsed, off-the-record, sincere, vernacular and non-standard”. Such a definition is easily understandable by the wider public outside of academia. However, it begs the question: who has the authority to make this distinction and who can validate these authenticity claims? Mary Bucholtz proposes instead the concept of authentication, or the outcome of constantly negotiated social and linguistic practices. Debates over what constitutes ‘authentic’ language in minority language settings are particularly noticeable, given the processes of revitalisation many of them are going through. This paper aims to move the discussion away from the purely linguistic when considering what authenticity means, and investigate the concept from a more speaker-centred perspective. The example of Breton in Brittany is taken as the case study here – what it means to speak Breton ‘authentically’, according to whom, and to which norms. In particular, attention is paid to the authentication process of negotiation and how different actors approach and manage this dynamic.