A phage or bacteriophage is a virus that infects and replicates within bacteria and archaea. The diversity and abundance of phages in the biosphere makes them prime model organisms for studying the principles of evolution and ecology. Some major areas of research related to phages include the study of phages as promoters of bacterial evolution, novel therapeutic agents, and sources of genetic and diagnostic tools. There are various biotechnological applications of phages and phage-derived proteins in industries such as health, food science and safety, and agriculture. A major therapeutic application of phage is phage therapy, which is seen as a potential therapy for treating pathogenic bacterial infections. In the food industry, phages are extensively used for securing food products and preventing food spoilage caused by bacteria. This book outlines the applications of bacteriophages in the field of biotechnology. It presents researches and studies performed by experts across the globe. The book will prove to be immensely beneficial to students and researchers in this field.