This chapter explores how digital twin technologies have evolved from engineering-oriented tools into multi-scalar policy instruments in urbanization, environmental policy, and governance. The main objective is to reveal how digital twins operate at global, national, and urban levels and how they redefine the concepts of sovereignty, governance, and spatial justice. Using a qualitative literature review, the research conducts a comparative analysis of key cases such as Destination Earth, Digital Tuvalu, Grenada, Bologna, Kaunas, and Vizzio Digital Singapore. The central assumption is that digital twins are not merely technical innovations but governance paradigms that generate data-driven public reasoning within decision-making processes. The findings indicate that while digital twins serve similar goals—sustainability, resilience, and participation—they produce different governance practices depending on institutional structures and societal engagement. The Digital Tuvalu project exemplifies digital sovereignty; the Bologna Civic Digital Twin highlights the digitalization of citizen participation; and Destination Earth represents the data-driven reconstruction of global environmental governance. The study contributes to the literature by offering a conceptual and methodological framework that redefines the technology–city–society nexus and positions digital twins as core instruments of an emerging digital governance ecosystem.