The article addresses the pressing issue of assessing and ensuring the spatial viability of municipalities in the extreme environment of the Republic of Sakha (Yakutia). The research aims to develop an original methodological framework for a comprehensive assessment of spatial viability, tailored to the specifics of northern and Arctic territories. The work analyzes theoretical and conceptual foundations, factors, types, and contemporary methods for assessing territorial viability. The scientific novelty lies in the synthesis of classical socio-economic geography approaches and modern spatial analysis methods (GIS, spatial statistics) to create an integrated assessment toolkit. The developed framework operationalizes classical geographical theories for the tasks of municipal-level management in an extreme environment, transforming them from an explanatory into an evaluative and instrumental model. The practical significance of the study is that the proposed methodology can be used by regional and municipal authorities for problem diagnosis, sustainability monitoring, justification of strategic decisions, and targeted regional policy aimed at preserving and developing settlements in the dispersed space of Yakutia.