Hypocrealean ascomycetes have a set of properties such as their unique mode of action by direct penetration through the cuticle, relatively ease to mass production, and their newly discovered ecological roles as endophytes and/or plant growth promoters which put them at the forefront of the global development of alternative control strategies. Firstly, the chapter addresses general aspects related to the natural occurrence and biodiversity, life cycle and delivery methods of the entomopathogenic fungi. Then using case studies, the chapter discusses the use of entomopathogenic fungi as biopesticides for the control of a wide range of insect and mite pests including locust and grasshoppers, soil dwelling insect pests, piercing and sucking insect and mite pests, store-grain pests, forestry pests, invasive pests, and medical and veterinary pests. Finally, the advantages and limitations of entomopathogenic fungi as biopesticides together with a market overview are provided, with a concluding section indicating also the possible future directions in the research on these fungi.