This study responds to calls to reexamine the L2 motivational self system framework in order to understand motivations to learn languages other than English. Specifically, we explore Indigenous Taiwanese students' heritage language learning motivation from a possible selves perspective. Following work on the rooted L2 self, the construct of the Indigenous heritage self is incorporated to capture the passion and conviction that motivates learners to maintain language use and revitalize cultural legacies. A nationwide questionnaire survey was administered to 293 indigenous Taiwanese high school students (aged 15-18). Exploratory factor analysis points to the need to include the Indigenous heritage self in an account of the motivation to learn endangered Indigenous languages. The composite elements of the Indigenous heritage self consist of goals focused on preserving the Indigenous language and cultures, as well as an emotional attachment to the heritage culture. Furthermore, multiple regression results show that learners' Indigenous heritage self and ideal future self are significant contributors to motivational intensity and classroom engagement. Findings indicate that community-based motivation is equally important as individual learners' idealized future images in motivating Indigenous language learning. The article concludes by suggesting curriculum initiatives that incorporate motivational strategy instruction aimed at developing an ideal self for speaking the Indigenous language, bridging classroom content and the cultural immersive experiences that students have outside formal environments.