Waqf (Islamic endowment) is one of the most profound socio-economic legacies of Islamic civilization. Rooted in the principle of voluntary asset dedication for public benefit, waqf has served as a cornerstone for institutional development in Muslim societies for over a millennium. The legacy is to describe how the foundational principles of waqf have been transmitted and adapted across different socio-legal contexts, producing parallel institutions that, while locally distinct, share their functional values. This paper explores waqf as a legacy, a foundational social institution embedded in Islamic thought and practice that continues to influence contemporary legal, economic, and governance structures. The study traces waqf’s historical evolution, its interrelationship with the Islamic concept of qard al-hasan (benevolent loan), and its intersection with land management, social justice, and state-building across different cultural and geographical contexts. Drawing from historical, legal, and institutional analysis, the article demonstrates how waqf inspired the emergence of similar mechanisms in global and Western societies, such as trusts and endowments. Furthermore, the article discusses the challenges facing waqf today, including asset fragmentation, governance issues, and underutilization. It also explores waqf’s potential as a strategic instrument for inclusive development, especially in education, healthcare, and social welfare. The research concludes that the waqf institution, when revitalized with modern governance tools and aligned with sustainability principles, offers a resilient and ethical model for long-term socio-economic empowerment and wealth redistribution.