The International Atomic Energy Agency (IAEA) has convened quadrennial symposia on isotope hydrology since 1963. In 2023 this symposium will celebrate 60 years of providing a unique opportunity to review the state-of-the-science, practical applications, and research trends and needs in isotope hydrology. Isotope hydrology contributes to a better understanding of the water cycle and has applications in water resources assessment and management, the study of past and future changes in the Earth’s climate as well as of climate impacts on the water cycle, and in forensic areas such as ecological, wildlife and food source traceability. This edition is the 16th symposium in the series and will be held at the IAEA’s Headquarters in Vienna, Austria. The symposium is aimed at facilitating the exchange of information and knowledge among water and environment professionals from developed and developing countries.