The rapidly growing field of astrochemistry focuses on the chemistry occurring in stars, planets, and the interstellar medium, bringing together elements of chemistry, physics, astrophysics, and biology. Astrochemistry describes the chemical history of the Universe, our solar system, and our planet. It explores in some detail the 'alien' chemistry occurring in interstellar gas clouds, the regions where stars and planets are formed, and also looks at the theoretical and experimental methods that allow us to carry out Earth-based studies of astrochemistry. The evolution of the Universe and the complex chemistry occurring both in interstellar space and in the planetary systems that form in these regions is explained primarily in terms of basic principles of physical chemistry. While there is plenty to interest the general reader, this book is aimed at intermediate to advanced undergraduates of chemistry and astrochemistry, highlighting many different aspects of physical chemistry and demonstrating their relevance to the world we live in. This book was written in conjunction with Atmospheric Chemistry: From the Surface to the Stratosphere, Grant Ritchie (2017) World Scientific Publishing.