The NI4OS-Europe Login service is the Authentication and Authorization Infrastructure (AAI) for the NI4OS-Europe infrastructure. It enables researchers to securely access and share common resources and services using identities from eduGAIN, the global network of academic identity federations. For users coming from the industry or citizen scientists who may not have access to eduGAIN, the NI4OS-Europe Login service supports additional trusted authentication providers, such as social networks, community identity providers and other platforms that can provide federated user identities. NI4OS-Europe Login allows connecting services using popular protocols, such as OpenID Connect and SAML, to securely authenticate and identify their users, organise them in groups, assign them roles and centrally manage access rights for accessing protected resources.