This book, Extremophiles: General and Plant Biomass Based Biorefinery, explores the potential of extremophiles in industries and biomass based biorefinery. The book sheds light on diversity and various applications of thermophiles, psychrophiles, halophiles, alkaliphiles and acidophiles for the production of value-added products including biofuels, extremozymes, etc. The chapters comprehensively emphasize the utility of extremophiles in sustainable biorefinery bioprocesses. This book is an integrated source of literature for scientists, engineers, academicians, and students working in the area of extremophiles, microbial technology and biorefinery.