This introductory chapter reviews the history of financing in the water and sanitation sector in the Global South, with a focus on the (potential) role of public banks to help meet Sustainable Development Goal 6. It provides a brief history of public banks in the water and sanitation sector, outlines debates about their meaning and significance in the sector and highlights key findings (positive and negative) from the case studies in the book. It argues that public banks can play a critical role in financing water and sanitation in the Global South, but that governments and multilateral development agencies must also significantly increase their investments in the sector.