This dissertation examines the results of two years of multi-sited ethnographic and linguistic fieldwork with indigenous Mapuche language activists in Chile. Research was conducted half in the Santiago metropolitan region, the epicenter of the Mapuche urban diaspora, and half in Temuco, the regional capital of the 9th region of Chile and the geographic and political center of Wallmapu, or the Mapuche ancestral territory as it is popularly envisioned by Mapuche people nowadays. Drawing on theories of discourse and social interaction, the dissertation charts new territory in the analysis of ethnic boundary making and the negotiation of identity and cultural heritage in a diasporic context. By methodologically centering the demographic and geographic diversity of the Mapuche diaspora in Chile, it charts the emergence of a diasporic Mapuche identity rooted in linguistic belonging and political activism. The analysis hews to a discourse-centered approach to how identities are established and maintained in order to generate insight into how speakers construct ethnic identity processually, continuously, in the cut and thrust of everyday life. From a semiotic and textual perspective, it tracks a range of interactional “events” as they instantiate—indexically invoke—cultural values, ideological essentializations that are invariably tied to social projects of specific kinds. Much of the dissertation focuses on the way that Mapuche identity, language and culture are imagined and constructed between the two poles of the Mapuche diaspora that were foregrounded by the methodological design. It provides an analysis of how the recent popularization of Mapuche language activism enables distinct opportunities for the imagination of Mapuche peoplehood in distinction to the prospect of a land-based territorial sovereignty of the kind that has animated Mapuche political activism for at least a quarter century. Moving between centers and peripheries and examining the ways that differently positioned individuals act and interpret other people, their actions, and the cultural categories that they meet in everyday social life, the dissertation aims to complicate the normative stereotypes of Mapuche cultural representation, probing deeper to understand how such stereotypes are made, remade, stabilized, and destabilized, all within the sphere of observable social behavior and its remediated precipitates.