AWS Organizations is an account management service that lets you consolidate multiple AWS accounts into an organization that you create and centrally manage. With AWS Organizations, you can create member accounts and invite existing accounts to join your organization. You can organize those accounts into groups and attach policy-based controls.

User Guide
Introduces you to AWS Organizations, helps you set up an organization by inviting other accounts to join, and shows you how to control access to your AWS resources by attaching policy-based controls.
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AWS Organizations section of AWS CLI Reference
Describes the AWS CLI commands that you can use to administer AWS Organizations. Provides syntax, options, and usage examples for each command.

API Reference
Describes all the API operations for AWS Organizations in detail. Also provides sample requests, responses, and errors for the supported web services protocols.