What is a Microsoft 365 tenant?
Also known as: M365 tenant, Microsoft cloud tenant
A Microsoft 365 tenant is the dedicated, isolated instance of Microsoft cloud services that an organization receives when it subscribes to Microsoft 365. It is the top-level boundary for identity, data, and configuration, so every user, SharePoint site, Team, mailbox, and policy belongs to exactly one tenant. Governance, security baselines, and compliance controls are applied at the tenant level, which makes the tenant the unit of oversight.
The tenant is the boundary that everything else in Microsoft 365 sits inside. Users, SharePoint sites, Teams, mailboxes, Power Platform environments, and every policy belong to exactly one tenant, and they cannot see across that boundary without explicit external-sharing or cross-tenant configuration.
Because the tenant is the unit of identity and configuration, it is also the unit of governance. Security baselines, compliance controls, and lifecycle policies are defined and measured at the tenant level, which is why administrators reason about risk one tenant at a time.
