Sclerospora is a genus within the Peronosporaceae family. It is a parasitic pathogenic organism that possesses thick-walled resting spores fused with the walls of oogonia. This plant pathogen is found worldwide and causes the growth of mildew on the surface of leaves, buds, young shoots, fruits, and flowers. The genus Sclerospora belongs to the subfamily Peronosporae along with the well-known genera Phytophthora, Plasmopara, and Peronospora. These genera are responsible for causing severe downy mildew diseases in crops. The Peronosporaceae family, which belongs to the Oomycota order Peronosporales, consists of eight genera that are morphologically and phylogenetically different. This family includes downy mildew pathogens, commonly known as graminicolous hosts, that infect plants in the Poaceae family. Graminicolous downy mildew causes significant crop losses in various regions of the world, particularly in tropical climates. Crops, such as maize, millet, sorghum, and sugarcane, are particularly susceptible to these mildew species. Downy mildews are obligate parasites that create intercellular hyphae and haustoria. Sporangia or conidia developed individually at the tips of branches. Sporangia produce zoospores upon germination, whereas conidia germinate through germ tube development. The thallus in Sclerospora is eucarpic, indicating that it produces an established filamentous coenocytic endoparasitic mycelium. This mycelium was composed of branched aseptate hyphae. Hyphae are freely branched and exist between cells. Downy mildew is a highly destructive disease that primarily affects millet, especially susceptible varieties. Over the past few decades, significant efforts have been made to address various issues related to understanding the biology and epidemiology of the downy mildew pathogen as well as the interaction between the pathogen and its host. These efforts have proven instrumental in the development of resistant cultivars and effective management of the disease. In this chapter, we provide a comprehensive review and discuss the genus Sclerospora, its classification, variability, pathogenicity, and management approaches.