Cancer immunotherapy aims to improve the immune system's natural ability to fight the disease. It artificially stimulates the immune system for treating cancer. It is a subspecialty of oncology and involves the application of the research on cancer immunology. Cancer cells have molecules called tumor antigens or antibodies present on their surface, which are often proteins or other macromolecules. These can be identified by the antibody proteins of the immune system. While normal antibodies bind to external pathogens, cancer immunotherapy uses modified immunotherapy antigens which bind to the tumor antigens. Thus, the cancer cells are marked and identified for the immune system to kill. This book outlines the processes and applications of cancer immunotherapy in detail. It is compiled in such a manner, that it will provide in-depth knowledge about the principles and practice of this field. As cancer immunotherapy is emerging at a fast pace, this book will help the readers to better understand the concepts of this field.