Which AWS service simplifies the management of IAM users and policies?

AWS Organizations simplifies the management of IAM users and policies across multiple AWS accounts, particularly in environments where multiple accounts are used. With AWS Organizations, you can centrally manage policies and governance across those accounts, making it easier to apply IAM roles and policies uniformly.

This centralization allows for more streamlined user management, enabling you to create and manage organizational units (OUs), which can help apply specific permissions and policies to entire groups of accounts, thus simplifying complex IAM setups.

In contrast, AWS Identity and Access Management (IAM) primarily focuses on individual account management, enabling you to create, modify, and delete IAM users and policies within a single AWS account. Therefore, while IAM is critical for user management, it does not offer the cross-account and organizational features that AWS Organizations provides.

AWS Directory Service serves a different purpose—it provides a managed directory for use with AWS services and applications, rather than focusing specifically on IAM user and policy management. AWS Security Hub aggregates and visualizes security alerts and compliance status from multiple AWS accounts but does not directly manage IAM users or policies.

Thus, AWS Organizations is particularly beneficial when handling multiple accounts, making it the correct choice for simplifying IAM management across a broader landscape.