Keeping in view of learner’s objectives in acquiring the recent knowledge in the subject and as per changing curriculum, an attempt is made to write a comprehensive book entitled “Essentials of animal Physiology”. The book contains 14 chapters covering cellular physiology and various organ system physiology such as neuro muscular, cardio vascular, renal physiology, hormones, homeostasis, hematology and reproductive physiology etc. The book is written in a simple and lucid way with several examples and illustrations with figures. This book is highly useful for both under-graduate and post -graduate students of Animal science and under-graduate students of Veterinary Medicine as the book is written following the syllabus from harmonized curriculum of undergraduate Animal science and Veterinary Medicine programmes. I appreciate my wife, Mrs. P. Sarada for providing me a constant source of inspiration to successfully accomplish this work. I would like to thank my daughters, P. Sudha and P. Vani who assisted me during this task. Dr.Surendra Nath P.