The Earth is a unique planet with conditions favourable for the emergence of life and its flourish. But even here, many habitats are characterized by conditions so extreme that it is a wonder how any live organisms can survive and reproduce. This especially concerns yeasts that for a long time were considered quite the opposite of what we regard as extremophilic/extremotolerant organisms. This chapter unites the recent data on extremely halotolerant and halophilic yeasts and polymorphic fungi, their ecology, and the discovery of novel fungal species. The major advances in our understanding of the adaptive strategies and mechanisms these extremotolerant fungi employ to thrive in hypersaline environments will be discussed.