This book presents the latest findings on the biodiversity, adaptation strategies, and biotechnological significance of extremophilic and extremotolerant yeasts. It is a valuable resource for researchers interested in the microbiology of these intriguing microorganisms. The book is divided into three parts: Part I gives an overview of prokaryotic and eukaryotic microbial life in extreme habitats. Part II focuses on the biodiversity, adaptation strategies and biotechnological applications of extremophilic yeasts, categorized according to the specific limiting abiotic parameters, such as thermotolerant (high temperature), psychrophiles and psychrotolerant (low temperature), acidophiles and acidotolerant (low pH), alkaliphiles and alkalitolerant (low pH), alkaliphiles and alkalitolerant (high pH), halophiles and halotolerant (high salinity), osmophiles and osmotolerant (low water activity), piezophilic and piezotolerant (high hydrostatic pressure), metallotolerant (high metal concentration), and oxidative stress-tolerant yeasts; Part III discusses the use of extremophilic yeasts in extreme foods and their biotechnological applications under extreme conditions. It is written for biologists, mycologists, chemists and all researchers whose field of study focuses on yeast biotechnology.