Osteogenesis imperfecta (OI) is a rare inherited connective tissue disorder and the most common cause of heritable bone fragility. Approximately 85–90% of cases result from pathogenic variants in COL1A1 and COL1A2 , typically following an autosomal dominant pattern of inheritance. The classification system proposed by Sillence et al. in 1979 originally described four clinical types and this has expanded to include additional subtypes with distinct phenotypic features and genetically heterogeneous causes, including autosomal recessive and X-linked recessive forms. The clinical spectrum of OI is highly variable, ranging from severe forms with multiple in utero fractures and perinatal lethality to milder presentations characterized by near normal stature and low fracture incidence. Early and accurate diagnosis is essential, particularly in the antenatal and neonatal periods, both for prognostic purposes and to differentiate OI from non-accidental injury. Management of OI is multidisciplinary, involving coordinated care from physiotherapists, occupational therapists, orthopaedic surgeons and metabolic bone specialists. Pharmacological treatment, particularly with bisphosphonates, has significantly improved outcomes by increasing bone mineral density, reducing fracture risk and enhancing quality of life in children. In contrast, there appears to be little role for bisphosphonates and dual energy X-ray absorptiometry scanning for adults with OI. This article provides an overview of bone biology, outlines the clinical features, classification and genetic variants of OI and highlights key principles in assessment and management.