The book gives a first consistent overview of methods and applications of ocean forecasting around the world. This sector of marine science and technology is developing rapidly due to the increasing need for reliable, multidisciplinary information about the marine system, allowing the sustainable usage of coastal resources and the mitigation of global change effects. Several chapters are devoted to the conceptual and theoretical bases of ocean forecasting, ranging from the design of observational and modelling systems, data assimilation techniques and numerical ecosystem modelling. The book also includes examples of modelling/forecasting systems currently in use or being set-up in the ocean for different space and time scales. The book is useful for advanced graduate students as well as scientists in related disciplines, as it enables them to understand the present level of knowledge and performance of existing forecasting systems.