Human-robot interaction (HRI) is a field which studies the interactions between a human and a robot. It is a multidisciplinary field that is based on the principles of artificial intelligence, robotics, human-computer interaction, design, natural language understanding and social sciences. Robots and humans are increasingly sharing the workspace due to the ever widening applicability of robots in different domains. The study of HRI becomes pertinent in this changing landscape, to improve utility and evaluate the benefits or risks of such close interaction. The goal of HRI is to create an easy and intuitive communication with the medium of gestures, speech and facial expressions. Research in HRI is exploring the boundaries of motion planning, human perception, human-robot coordination, etc. An emerging direction of robot application has been the use of assistive robots in schools, homes and hospitals to aid in physical activities, improve education, or act as companions. Military utility, space exploration, rehabilitation and elderly care, search and rescue, etc. are the other domains where HRI can be vital. There has been rapid progress in human-robot interaction and its applications are finding their way across multiple industries. This book traces the progress of this field and highlights some of its key concepts and applications. Researchers and students in this field will be assisted by this book.