Reaction mechanisms are a fundamental part of the study of organic chemistry, and the aim of this book is to help you to understand them. Sometimes Organic reaction mechanisms are perceived to be an incoherent but in fact there are principles underlying them that make them much easier. Reading this book should of these principles give to you a grasp, reading this book should give you mastery of these principles. I am feeling great pleasure to presenting the first edition of book entitled “ORGANIC REACTION MECHANISM”. In the present book all the associated steps of Reaction Mechanism are given to very simple and lucid manners.  Throughout the book, the content matter of concept in each chapter had been presented in a systematic way and also in a systematic way and also in a language easy enough to be followed by the students. My special thanks go to publishers and the printer for their Co-operation and efficiency with which they have brought out this book in the present nice form.  I shall be highly obliged, if the readers send to us their constructive Criticism and suggestions which we shall be used in the publication of the next edition.