A federated identity in information technology is the means of linking a person's electronic identity and attributes, stored across multiple distinct identity management systems.

Federated identity is related to single sign-on (SSO), in which a user's single authentication ticket, or token, is trusted across multiple IT systems or even organizations. SSO is a subset of federated identity management, as it relates only to authentication and is understood on the level of technical interoperability, and it would not be possible without some sort of federation.

In information technology (IT), federated identity management (FIdM) amounts to having a common set of policies, practices and protocols in place to manage the identity and trust into IT users and devices across organizations.

Single sign-on (SSO) systems allow a single user authentication process across multiple IT systems or even organizations. SSO is a subset of federated identity management, as it relates only to authentication and technical interoperability.

Centralized identity management solutions were created to help deal with user and data security where the user and the systems they accessed were within the same network – or at least the same "domain of control". Increasingly, however, users are accessing external systems which are fundamentally outside their domain of control, and external users are accessing internal systems.

The increasingly common separation of the user from the systems requiring access is an inevitable by-product of the decentralization brought about by the integration of the Internet into every aspect of both personal and business life. Evolving identity management challenges, and especially the challenges associated with cross-company, cross-domain access, have given rise to a new approach to identity management, known now as "federated identity management".

Technologies used for federated identity include SAML (Security Assertion Markup Language), OAuth, OpenID, Security Tokens (Simple Web Tokens, JSON Web Tokens, and SAML assertions), Web Service Specifications, and Windows Identity Foundation.