The fungal genus Botrytis is the focus of intensive scientific research worldwide. The complex interactions between this pathogen and the plants it infects and the economic importance of the diseases caused by Botrytis (principally grey mould) on more than 1400 species of cultivated plants pre- and post-harvest, render this pathogen of particular interest to farmers, advisers, students and researchers in many fields worldwide. This 20-chapter book is a comprehensive treatise covering the rapidly developing science of Botrytis and reflecting the major developments in studies of this fungus. It will serve as a source of general information for specialists in agriculture and horticulture, and also for students and scientists interested in the biology of this fascinating, multifaceted phytopathogenic fungal species.