AWS service for centrally managing multiple AWS accounts. Like having a corporate headquarters that manages all branch offices with consistent policies.
Large enterprises use AWS Organizations to apply security policies and manage billing across hundreds of AWS accounts.
All four provide hierarchical governance across multiple accounts/projects/subscriptions. AWS Organizations groups AWS accounts into organizational units (OUs) and applies policies (SCPs) and consolidated billing. Azure uses Management Groups to organize subscriptions and apply Azure Policy/RBAC. GCP uses an Organization with Folders and Projects plus IAM/Org Policies. OCI uses Compartments and IAM policies to segment resources and control access.