Chemical engineers play a pivotal role in designing and operating process plants. Based on the nature of the substances involved, engineers must navigate Gas?Liquid, Gas?Solid, Liquid?Liquid, Liquid?Solid and Solid?Solid systems. These operations significantly influence production costs in the process industry. Hence, it is imperative for chemical and process engineers to possess a strong foundation in mass transfer principles and their applications. This book is designed to equip undergraduate students of Chemical Engineering and Production and Industrial Engineering with the knowledge needed to tackle real?word challenges. This textbook comprises thirteen chapters, each focusing on theoretical concepts as well as practical applications of mass transfer. It is designed for a two-semester, four-credit course and aligns with the mass transfer course syllabus of most Indian universities. The primary goal of the book is to guide budding chemical engineers in analyzing processes and selecting appropriate mass transfer techniques for component separation. Topics covered include diffusion, interphase mass transfer, humidification, drying, crystallization, absorption, distillation, extraction, leaching, adsorption, and advanced separation methods. An overview of commonly used equipment in mass transfer operations is also presented.