Abstract: This paper presents a synthesis of the results of a study we carried out in 2009 that describes from an ethnolinguistic point of view the characteristics of the Mapuche language and its native speakers in the urban context of Santiago, Chile. Loyalty towards the language, its urban vitality, and the social representations that the Mapuche have constructed about their native language are considered, with particular emphasis on the sociocultural determinants that define these issues. In this way, we attempt to link the reflection and social representation that the Mapuche have of their language with the processes of identity in the city, a discursive hub for what defines the essence of “being Mapuche.” In addition, we incorporate data about effective (as opposed to declared) linguistic competence, both syntactic and lexical, in order to have data regarding the role that actual linguistic knowledge plays in the definition of what it means to “be Mapuche” and its use as a source of status and power by the Mapuche communities. From this point of view, a low degree of effective competence in the language can be seen which corresponds to its low language vitality and contrasts with its high symbolic value as a marker of identity and status.