provides an overview of our contemporary understanding of the Indian Ocean (geology, atmosphere, ocean, hydrology, biogeochemistry) and its role in the climate system. It describes the monsoon systems, Indian Ocean circulation and connections with other ocean basins. Climatic phenomena in the Indian Ocean are detailed across a range of timescales (seasonal, interannual to multi-decadal). Biogeochemical and ecosystem variability is also described. The book will provide a summary of different tools (e.g., observations, modeling, paleoclimate records) that are used for understanding Indian Ocean variability and trends. Recent trends and future projections of the Indian Ocean, including warming, extreme events, ocean acidification and deoxygenation will be detailed. The Indian Ocean is unique and different from other tropical ocean basins due to its geography. It is traditionally under-observed and understudied, yet plays a fundamental role for regional and global climate. The vagaries of the Asian monsoon affect over a billion people and a third of the global population live in the vicinity of the Indian Ocean. It is also particularly vulnerable to climate change, with robust warming and trends in heat and freshwater observed in recent decades. Advances have recently been made in our understanding of the Indian Ocean’s circulation, interactions with adjacent ocean basins, and its role in regional and global climate. Nonetheless, significant gaps remain in understanding, observing, modeling, and predicting Indian Ocean variability and change across a range of timescales. As such, this book is the perfect compendium to any researcher, student, teacher/lecturer in the fields of oceanography, atmospheric science, paleoclimate, environmental science, meteorology and geology, as well as policy managers and water resource managers.