Introduction Water plays a fundamental, critical role in every economy and thus is very important in almost all aspects of the human endeavor. It is undoubtedly the most precious resource that exists on our planet. Without water, life on earth would be non-existent: it is essential for everything on our planet to grow and prosper. Although we as humans recognize this fact, we disregard it by polluting our rivers, lakes and ocean from time to time. Subsequently we are slowly but surely harming our planet to the point where organisms are dying at a very alarming rate. In addition to innocent organisms dying off, our drinking water has become greatly affected as is our ability to use water for recreational purposes, resulting to the global water crisis. According to the statistics, although water comprises over 70% of the Earth's surface, less than 1% of the planet's water is available for human consumption. More than 1.2 billion people have no access to safe drinking water. The situation is becoming worse and worse seemingly. Currently, more than 40% of the world's population lives in conditions of water stress and this percentage is estimated to grow to almost 50% by 2025.2 Current threats to freshwater resources are two-fold: increased use, and declining quality as a result of anthropogenic sources of pollution. Future threats include climate change, and population growth increasing the worldwide demand for water. Additionally, history shows the intimate connection between economic and social development of a society and adequacy and dependability of water. Due to the abovementioned reasons, the protection of water is really one of the crucial issues to be solved in hand, and it is quite necessary to research the mechanisms of the water legal system as a legal researcher who cares for the benefits of the humankind. So to speak, in order to combat water stress, we must understand the problems and become a part of the solution. All kinds of legal systems must have their own principles, which can be viewed as the foundations of their whole legal structures, and a kind of instructional instrument for their interpretation, implementation and development as well. It is the same as in the case of European Union (EU) water law. This thesis is designed to examine the nature and role of main principles of EU water law, including the key concepts and current issues on the understanding of the principles as well the future of EU water law. By way of analyzing and interpreting the water law in EU, a comparative approach is adopted through the introduction o International Water Law (IWL), for understanding this issue better.