Medulloblastoma is a form of brain cancer that mainly arises during infancy and childhood. Our understanding of this disease has transitioned rapidly; what was once thought of as a single disease entity is now known to be a compendium comprising at least four distinct subtypes of tumour (Wnt, sonic hedgehog [SHH], group 3, and group 4 medulloblastomas) that have characteristic molecular signatures, distinctive clinical features, and are associated with different outcomes. Importantly, medulloblastomas occurring in infants (aged up to 3 years) and adults have unique characteristics, which distinguish the disease from that seen in children aged >3 years. Accordingly, modern treatment approaches in medulloblastoma integrate the molecular and clinical features of the disease to enable provision of the most-effective therapies for each patient, and to reduce long-term sequelae. This Review discusses our current knowledge of medulloblastoma. In particular, we present the genetic and histological features, patient demographics, prognosis, and therapeutic options for each the four molecular tumour subtypes that comprise this disease entity. In addition, the unique features of medulloblastoma in infants and in adults, as compared with childhood and/or adolescent forms, are described.