In Islamic civilization, one of the most persistent systems for promoting social welfare and economic fairness is the idea of waqf, or Islamic endowment. Long before the emergence of contemporary state welfare systems, Waqf organizations provided funding for social infrastructure, healthcare, education, and water systems, establishing the groundwork for sustainable communal development. This paper explores how Waqf revitalization can provide a revolutionary paradigm for accomplishing 21st-century global sustainability objectives. The study places Waqf in the larger context of ethical finance, social innovation, and sustainable development by utilizing qualitative and comparative analysis. Through an examination of case studies from Malaysia, Indonesia, Turkey, and new projects in Nigeria, the study shows how productive Waqf can promote social resilience, environmental responsibility, and economic inclusion when it is in line with modern financial tools and the Sustainable Development Goals (SDGs) of the UN. According to the research findings, Waqf offers a distinctive institutional and moral model for fusing spirituality with contemporary development paradigms because it is a faith-based and values-driven organization. The study comes to the conclusion that Waqf governance can become a worldwide tool of ethical finance and sustainable transformation by being revived and modernized through legal reform, digital transparency, and cross-sector collaboration. The study adds to the current body of knowledge on Islamic social finance and presents Waqf as a feasible route to a more just, inclusive, and sustainable future for all people.