Geopressure drives fluid flow and is important for hydrocarbon exploration, carbon sequestration, and designing safe and economical wells. This concise guide explores the origins of geopressure and presents a step-by-step approach to characterizing and predicting pressure and least principal stress in the subsurface. The book emphasizes how geology, and particularly the role of flow along permeable layers, drives the development and distribution of subsurface pressure and stress. Case studies, such as the Deepwater Horizon blowout, and laboratory experiments, are used throughout to demonstrate methods and applications. It succinctly discusses the role of elastoplastic behaviour, the full stress tensor, and diagenesis in pore pressure generation, and it presents workflows to predict pressure, stress, and hydrocarbon entrapment. It is an essential guide for academics and professional geoscientists and petroleum engineers interested in predicting pressure and stress, and understanding the role of geopressure in geological processes, well design, hydrocarbon entrapment, and carbon sequestration.