Over the past two decades, advanced technologies and space missions have completely transformed our understanding of potential life beyond Earth. The resulting field, astrobiology, has become a multidisciplinary scientific discipline, encompassing many of the natural sciences and having implications for many areas of research. This book presents an introduction and overview of astrobiology. It deals with a wide range of fields, from the search for signs of life on planets in our solar system, to the discovery of exoplanets in distant solar systems and assessing the potential for life there. The book is based on the course of the same name that the author taught for more than two decades at the Hebrew University, and the course recorded on YouTube in the Cornerstones program, which has accumulated tens of thousands of views. The book is accessible not only to students of natural sciences, but to any reader who wants to learn about and understand the fascinating possibilities of life on other worlds.