An organizational unit (OU) is a subdivision within an Active Directory to which you can place users, groups, computers, and even other organizational units. Organizational units can be created to mirror an organization's functional or business structure. Each domain can implement its own organizational unit hierarchy. If an organization contains several domains, there may be organizational unit structures in each domain which are independent of the structures in the other domains.

The term "organizational unit" is often shortened to "OU" in casual conversation. The organizational units within the School of Education’s AD domain are "WCER" and "SOEIT".