The book titled Water Quality – An Emerging Concern for a Sustainable Future was conceived to underscore the necessity of an immediate focus on water quality worldwide, as it has proven to be a global threat to humankind, ecosystems, and biodiversity. It may seem that human society is more concerned with global climate change, nuclear threats, and the rise of deadly diseases, including viruses, than with water quality, which is believed to be not so critical. However, growing scientific evidence clearly shows that rapid deterioration in global water quality significantly affects human health, the collapse of aquatic ecosystems, and food security, while imposing significant financial burdens on societies and triggering geopolitical tensions or even climate (water) refugees. This title has attracted many high-quality papers that have been evaluated for publication, thus confirming the scientists' concern and dedication to reversing the global negative trend and ensuring a sustainable future with clean water for future generations.