Federation.
An identity pattern where one identity provider authenticates a user on behalf of another, the federated party trusts the upstream IdP's assertion.
Federation is older than OAuth and OIDC, early SAML deployments in the mid-2000s established the model that every modern enterprise IdP and B2B SaaS still uses. The protocol set has changed; the trust pattern hasn't.
Common questions
Is federation the same as SSO?
What protocols enable federation?
What is chained federation?
Related terms
In the guides
B2B SaaS Identity: Organizations, SSO, SCIM, and the Enterprise Sales Checklist
How to design B2B SaaS identity: Organizations, Enterprise SSO with SAML and OIDC, SCIM provisioning, audit logs, and the IT-admin features that close enterprise deals.
Enterprise SSO: SAML vs OIDC, and How to Pick
SAML and OIDC are the two protocols that dominate enterprise SSO. A practical comparison, when each is the right answer, and the IdP-side considerations that determine the choice.