Over the past decade the significant advances in real-time ocean observing systems, ocean modelling, ocean data assimilation and super-computing has seen the development and implementation of operational ocean forecast systems of the global ocean. At the conclusion of the Global Ocean Data Assimilation Experiment (GODAE) in 2008 ocean analysis and forecasting services were being supported by 12 international centres. This book is about ocean forecasting - a maturing field which remains an active area of research, and includes such topics as ocean predictability, observing system design, high resolution ocean modelling and ocean data assimilation. It presents the introduction to ocean forecasting which provides a foundation for new opportunities in areas of coupled bio-geochemical forecasting and coupled atmosphere-wave-ocean forecasting. The book describes an updated account of research and development to improve forecast systems, determining how best to service the marine user community with forecast information as well as demonstrating impact to their applications. It also discusses operational centres that are now supporting a range of real-time ocean services including online graphical and data products for their user communities and their feedback on the quality of information. The contents of this book are aimed at early career scientists and professionals with an interest in operational oceanography and related ocean science. There are excellent opportunities for exciting careers in the emerging field of operational oceanography in order to address current and future challenges as well as provide the supporting services to a rapidly growing user community.