Which AWS service offers multi-account management?

AWS Organizations is the correct choice for multi-account management because it allows you to create and manage multiple AWS accounts under a single organization. This service provides the ability to centrally manage billing, apply policies, and simplify the management of multiple accounts. With AWS Organizations, you can group accounts into organizational units (OUs), apply service control policies (SCPs), and enable consolidated billing across accounts. This helps organizations maintain security, compliance, and governance while managing resources effectively.

Other services like AWS IAM (Identity and Access Management) focus primarily on managing permissions and roles for users and services within a single AWS account, rather than managing multiple accounts. Amazon S3 (Simple Storage Service) is used for cloud storage and does not have any features related to account management. AWS CloudFormation is a service for deploying infrastructure as code, allowing you to manage resources but not specifically focused on multi-account setups. Thus, AWS Organizations stands out as the service designed explicitly for managing multiple AWS accounts effectively.