Over the past thirty years, Latin America has been the site of substantial efforts to privatize urban water and sanitation services. As a consequence of these privatization experiments, the state shifted from running water utilities to a regulatory role while multinational private firms came to occupy service provider roles that had traditionally been in the public sector. In this dissertation, I compare this process in Chile and Argentina, focusing on the Santiago Metropolitan Region and Greater Buenos Aires since the late 1980s to the present. I show that in Chile, state-run water utilities achieved relatively high performance with respect to extending access to running water and sewerage connections before full-scale privatization went forward. The fact that they were high performing made them not only more attractive to private investors but also more likely to be interpreted as proof of privatization success later on. By contrast, in Argentina, where connections to running water and sewerage services were low and the waterworks system faced many problems, especially in the informal settlements and marginalized communities of Greater Buenos Aires, the experiment failed and private companies could not step in to fill gaps created by weak state capacity despite the expectations set up by the narrative of pro-market supporters. Still, the years of failed privatization inadvertently led the government to eventually pay attention to water and sanitation again, pouring funding into new public works alongside the creation of a new public sector company. I locate this narrower water and sanitation privatization story in the political and economic transformations unfolding in the two countries, considering social responses to water privatization, and showing that whereas both the efforts to deepen privatization, as in Chile, or return water to the public sector, as in Argentina, were mainly state-led, the shifts created new ways for civil society groups to engage with the state and private multinational actors when making claims about the provision of basic services and articulating socioeconomic rights. The research is based on more than twelve months of fieldwork in Chile and Argentina to gather primary and secondary historical sources as well as to carry out sixty-five semi-structured interviews with knowledgeable respondents involved on various sides of the water privatization process, including government officials, representatives from the private sector, and activists.