Multitenant authentication refers to running a single application instance that serves multiple customer organizations. This approach reduces operational costs but increases complexity by requiring isolation while supporting organization-specific authentication needs. Common scenarios include cross-organization access, organization-specific security policies, and access management. To implement multitenant authentication, teams can choose between building custom admin tooling, manual configuration, or using a dedicated authentication platform like WorkOS, which provides pre-built solutions for enterprise auth management, including dynamic SSO configuration, SCIM provisioning, and self-service administration. However, teams often make common pitfalls such as assuming single organization membership models, missing organization context, hard-coding SSO configurations, mixing authentication contexts, underestimating directory sync, and insufficient access controls. To get started building multitenant auth, teams can leverage platforms like WorkOS to focus on core product features instead of wrestling with authentication infrastructure.