Identity federation extends identity trust across organizational boundaries — a user authenticated at Company A is trusted by Company B without separate credentials. SAML 2.0 and OIDC are the protocols.
Federation enables cloud SSO across enterprises. Trust is established via metadata exchange and certificate sharing. SAML: enterprise web SSO. OIDC: modern apps and APIs (built on OAuth 2.0). Key use case: employee accessing partner systems or SaaS apps with corporate credentials.