<p>Hydrogen is increasingly recognized as a key building block of the global energy transition; however, conventional hydrogen production techniques are still resource-intensive and environmentally damaging. Concurrently, wastewater flows produced in huge quantities from municipal and industrial activities are an underexploited resource with ample potential for organic matter, nutrients and recoverable energy. This paper critically reviews the recent developments in sustainable production of hydrogen from wastewater in the context of a circular economy. The study shows a comparative and integrative evaluation of biological, electrochemical and thermochemical hydrogen production routes in various waste water sources, such as municipal, agri-industrial and heavy industrial waste water. Key performance indicators like hydrogen yield (HY), hydrogen production rate (HPR), energy efficiency, techno-economic feasibility and life-cycle environmental impacts are systematically synthesized. Particular emphasis is laid on the association with hydrogen recovery to remediate wastewater, to valorize resources, and to be compatible with Sustainable Development Goals (SDG) 6 and 7. The review also appraises existing limitations associated with scalability, electricity costs, durability of catalysts, and policy support, and identifies important research gaps that hinder large scale implementation. By considering wastewater not as a waste stream but as one of the strategic feedstocks for green hydrogen, this review presents a consolidated knowledge base to guide researchers, industry stakeholders and policy makers towards integrated and sustainable hydrogen-wastewater systems.</p> Graphical Abstract <p></p>