Introduction Water is a resource that triggers profound conflicts and close collaboration, a source of deep injustices, and fierce struggles for life. In many regions of the world, rising demand and declining availability of adequate-quality water foster severe competition and ferocious clashes among different water uses and users. People also suffer from flooding; contamination caused by industry and mining; privatization of public water utilities; corruption; and displacement by large dam projects. Climate change intensifies most human-made water problems. In struggles for water security, the poor tend to lose (e.g. Crow et al., 2014; Escobar, 2006; Harvey, 1996; Perreault et al., 2011). Through exemplary cases, the chapters in this book show how new competitors - including megacities, mining, forestry, and agribusiness companies - demand and usurp a mounting share of available surface and groundwater resources (e.g., Donahue and Johnston, 1998; GRAIN, 2012). Water deprivation and water insecurity affect marginalized urban households, and rural smallholder families and communities. In many regions, this poses profound threats to environmental sustainability and local and national food security (e.g., Escobar, 2008; Mehta et al., 2012; Mena et al., 2016). Such proliferating problems of material and social “water injustices” provide the backdrop for this book. Distribution of access water rights and water-related decision-making is extremely skewed. Smallholder communities’ water-based livelihoods and rights in many countries of the global South are constantly threatened by bureaucratic administrations, market-driven policies, and top-down project intervention practices. Despite the fact that water injustices have existed throughout human history, water justice problems and related policy interventions have changed rapidly over recent decades (Zwarteveen and Boelens, 2014). For instance, rather than focusing on simply enlarging water flows through new hydraulic engineering projects, new perspectives focus on water saving and conservation (Vos and Marshall, 2017; Zwarteveen, 2015). New scientific fields and water professionals have entered the water policy-making and intervention worlds to accompany (increasingly high-tech) hydraulic engineering (Buscher and Fletcher, 2015; Goldman, 2007, 2011). Also, climate change threats and water-related disasters have changed science and policy debates and water funding projects related to issues such as “mitigation and adaptation,” flood control and drought prevention (Heynen et al., 2007; Lynch, 2012; Martínez-Alier, 2002). Further, global neoliberalism has assured that water development and governance are no longer seen as the exclusive realm of the state, with water knowledge and authority concentrated in powerful public agencies (Hommes et al., 2016; Loftus, 2009; Zwarteveen, 2015).