Indigenous Peoples are struggling for water justice across the globe. These struggles stem from centuries-long, ongoing colonial legacies and hold profound significance for Indigenous Peoples' socioeconomic development, cultural identity, and political autonomy and external relations within nation-states. Ultimately, Indigenous Peoples' right to selfdetermination is implicated. Growing.out of a symposium hosted by the University of Colorado Law School and the Native American Rights Fund in June 2016, this Article expounds the concept of "indigenous water justice" and advocates for its realization in three major transboundary river basins: the Colorado (U.S./Mexico), Columbia (Canada/U.S.), and Murray-Darling (Australia). The Article begins with a novel conceptualization of indigenous water justice rooted in the historic United Nations Declaration on the Rights of Indigenous Peoples (UNDRIP)-specifically, UNDRIP's foundational principle of selfdetermination. In turn, the Article offers overviews of the basins and narrative accounts of enduring waterjustice struggles experienced by Indigenous Peoples therein. Finally, the Article synthesizes commonalities evident from the indigenous water-justice struggles by introducing and deconstructing the concept of "water colonialism." Against this backdrop, the Article revisits UNDRIP to articulate principles and prescriptions aimed at prospectively realizing indigenous water justice in the basins and around the world.