This study examines hygeralai as a system of knowledge and socio-ecological governance practiced by the Indigenous community of Luang Island, Southwest Maluku, within the broader context of global climate change and increasing coastal development pressures. Against the backdrop of rising sea temperatures and ocean acidification that significantly affect coastal ecosystems, the study positions hygeralai not merely as a customary tradition, but as a normative and cosmological framework that structures sustainable human–nature relations. The research employs a qualitative ethnographic design grounded in ecological anthropology and the socio-ecological systems (SES) framework. Data were collected through in-depth interviews, participant observation, documentation, and spatial analysis using Geographic Information Systems (GIS). Sampling followed the principle of data saturation, reaching a saturation level exceeding 90%. Data analysis proceeded through domain, taxonomic, componential, and thematic stages to identify the normative, ecological, and social dimensions embedded in hygeralai practices. The findings indicate that hygeralai is rooted in linguistic transformation and local cosmology that conceptualize the sea as both a sacred domain and a communal resource. The system regulates seasonal harvesting closures and openings, restricts fishing gear, and institutionalizes collective responsibility for maintaining ecological balance. Coral reef conditions in the Luang region, including Metiamarang Island, remain relatively healthy, characterized by low levels of degradation and high biodiversity. Nevertheless, ecosystem sustainability faces internal challenges, such as unstructured waste management, as well as external threats including illegal fishing, destructive fishing practices, and the impacts of global climate change. The study demonstrates that hygeralai represents a spiritually grounded environmental ethic integrating historical, linguistic, and ecological dimensions within a community-based governance system. It contributes to the development of marine resource management models for Indonesia’s outermost small islands by emphasizing the integration of local knowledge, institutional support, and adaptive policy responses to global environmental change.