This book provides a comprehensive introduction to the physical phenomena that result from the interaction of the sun and the planets - often termed space weather. Physics of the Space Environment explores the basic processes in the Sun, in the interplanetary medium, in the near-Earth space, and down into the atmosphere. The first part of the book summarizes fundamental elements of transport theory relevant for the atmosphere, ionosphere and the magnetosphere. This theory is then applied to physical phenomena in the space environment. The fundamental physical processes are emphasized throughout, and basic concepts and methods are derived from first principles. This book is unique in its balanced treatment of space plasma and aeronomical phenomena. Students and researchers with a basic mathematics and physics background will find this book invaluable in the study of phenomena in the space environment.