Water Reuse in Singapore: The New Frontier in a Framework of a Circular Economy?As part of the circular economy, there is increasing interest internationally in water reuse, reclaimed water or recycled wastewater. This interest responds to water scarcity concerns at present and to demands projected for the resource by all sectors in the future, which will surpass freshwater available. It also responds to the incentive to close the water loop and extend the lifetime of water resources through longer use, with the related economic, social and environmental benefits. In this chapter, we discuss water reuse in Singapore where it has been implemented since 2003 for potable and non-potable uses, putting in practice the concept of circular economy. We argue that water reuse is part of a comprehensive framework of water security in the city state that considers long-term policy, planning, management, governance and technological developments. As essential foundations for a reliable water reuse system, we discuss water resources management related institutional and legal frameworks and their evolution over time. We conclude that water reuse is one of the most important pillars for Singapore to provide safe and reliable water sources at present and looking towards the future.