Stemphylium is a fungal genus classified in the phylum Ascomycota. Stemphylium is a filamentous fungus that is extensively dispersed globally and is commonly found as an endophyte, epiphyte, or saprophyte, and a plant pathogenic species, frequently present on dying plants and in the soil. Pleospora serves as a teleomorph of Stemphylium. Stemphylium undergoes both sexual and asexual reproduction during its lifecycle. Under ideal circumstances, it undergoes asexual pheodictyospore production by proliferating conidiophores and apically conidiogenous cells. Stemphylium species can function as plant pathogens, leading to the development of disease in different types of crops. Stemphylium is responsible for causing severe diseases, such as leaf blight, in onion and lentil plants. This chapter provides an in-depth examination of the ecology and pathology of Stemphylium. It covers several aspects, such as classification, global distribution, transmission, host range, symptomatology, pathogenicity, isolation and identification, detection, epidemiology, economic importance, and control measures. To protect crops and reduce the economic impact of Stemphylium infection, it is crucial to have an in-depth understanding of the complexities of this destructive plant disease.