SIOP may refer to: International Society of Paediatric Oncology Sales Inventory Operations Planning, an integrated business management process Sheltered Instruction Observation Protocol, a research-based observation instrument used to measure sheltered instruction Single Integrated Operational Plan, the tactical blueprint for the deployment of nuclear weapons by the United States Society for Industrial and Organizational Psychology, a division of the American Psychological Association for I/O psychologists Steroid-induced osteoporosis, a bone disease that leads to an increased risk of fracture