Whether people have access to drinking water, irrigation water and sanitation or not, whether water resources are used sustainably or overexploited, and whether emerging challenges for the water sector - such as adaptation to climate change are tackled or not, in the end relies on politics. The importance of the political sphere for understanding and solving water sector problems is the basic rationale of this book, which is the outcome of the Fifth Dialogues on Water, organised at the German Development Institute, Bonn. It is not the first time that the Dialogues on Water have touched upon water politics. But these Dialogues, unlike earlier ones, focussed on the political processes of policy formulation and the strategic behaviour of the actors involved. The papers assembled in this book analyze debates and investigate water politics at the international, national and local level, each considering different aspects or different elements of policy formulation and implementation processes from a variety of disciplinary backgrounds. They examine policies as results from power plays of state and non-state actors alike over water resources and modalities of water service delivery and as a function of their respective means of influence. While some authors follow a constructivist line, elaborating on how global norms on water-related issues evolve and how international debates influence them, others apply a political economy or public choice perspective, adhering to a rational actor approach. In line with the general focus of the Dialogues on Water, specific attention is devoted to implications for development cooperation.