This is the first of a divided two-part softcover edition of the "Lectures in Astrobiology Volume I" containing the sections "General Introduction", "The Early Earth and Other Cosmic Habitats for Life" and "Appendices" including an extensive glossary on Astrobiology. "Lectures in Astrobiology" is the first comprehensive textbook at graduate level encompassing all aspects of the emerging field of astrobiology. Volume I of the Lectures in Astrobiology gathers a first set of extensive lectures that cover a broad range of topics, from the formation of solar systems to the quest for the most primitive life forms that emerged on the Early Earth.