This research deals with water as a fundamental right and its importance for humanity, for the existence of man and all kinds of life on the planet. It addresses the historical evolution of Fundamental Rights and the principles and aspects of Environmental Law as a basis for the configuration of water as a public and common good. The global situation of water resources, the problems surrounding scarcity, waste, pollution, commercialisation, economic interests and the possibility of international conflicts, as well as the need for current and permanent legislation. It also presents the Brazilian legislative competence of waters and the National Policy on Water Resources. Finally, some concluding remarks, where the need for education and environmental information in awareness that provides preventive care and sustainability of water sources and the environment itself is glimpsed. It is also concluded that water is essential to human life and that, therefore, it is part of the fundamental rights of man, in addition to precepting the dignity of the person and the healthy quality of life.