“Transmedia Arts Activism and Language Revitalization: Critical Design, Ethics and Participation in Third Digital Documentary” is a practice- and theory-based dissertation focused on indigenous and minority language endangerment and revival through explorations of case studies and personal stories from Taiwan and Hawai’i. It consists of the feature-length documentary Tongues of Heaven, the companion web application Root Tongue: Sharing Stories of Language Identity and Revival, and a written component describing the theoretical and methodological underpinnings of the critical arts practice engaged in these works. This dissertation examines a major thematic in the documentary, which is its engagement with the term “native”—as topic, object and subject—and its attending discourse and practices of authenticity, ethnography, salvage ethnography, and autoethnography. It details the materialization of the documentary Tongues of Heaven through an analysis of the (post)colonial historical circumstances that led to its production; its collaborative cross-boundary and transnational mode of production; and the Third Cinema, experimental and feminist approaches that inspired its media praxis. I then discuss the under-acknowledged process of film/video editing by analyzing the limits of postructuralist endeavors in representation, and theorizing the concept of interval, as it exists between and within shots, as a productive spectatorial intervention. In the effort to extend public engagement with documentary issues via digital and online technologies, I initially survey the discursive and technological interventions into the notions of “public” and “participation,” and how offline and online spheres of publics, counterpublics and community operate, intersect and interact to create multiple ways of being together in community, as a public and with oneself. I conclude with an analysis of the critical arts practice in the design and production of the Root Tongue transmedia activist art platform to pilot new collaborations in documentary and new digital media for a third digital documentary practice that provides space for new projects on race and online culture, indigeneity and virtuality, and on ethics and digital publics. Overall, this dissertation contributes to and expands the field of autoethnographic media production while critically considering and harnessing digital and Internet technologies as viable creative, cultural and social tools with unique discursive potentials.