Okta - Enterprise-grade identity management for all your apps, users & devices
Keycloak - Open Source Identity and Access Management for modern Applications and Services.
Auth0 - Auth0 is a program for people to get authentication and authorization services for their own business use.
Shibboleth - standards based, open source software for web single sign-on across or within organizational...
OneLogin - On-demand SSO, directory integration, user provisioning and more
CAS - Apereo CAS - Enterprise Single Sign On for the Web