There are paid services like Stormpath (https://stormpath.com) or you can use Oauth2 to make the so-called "social login" where users can use their social network accounts such as Facebook, twitter in addition to github, Google.
Make a careful analysis of this need before implementing it as it may be more laborious in the end than creating your own. If it’s just for user authentication Oauth2 might be interesting, but if added to this you need to control access to system modules, permissions and so on it won’t help you.
Perhaps the most famous service today is the Facebook login: https://developers.facebook.com/docs/facebook-login?locale=pt_BR. That is, the user would enter your application by logging in/password from it on Facebook. But I have no doubt that creating this integration in your application is as, if not more, difficult and time-consuming as building your own access control layer.
– C. Bohok
If the system is for desktop, use a desktop component, native to Delphi, there are several, a very good and 'di gratis', widely used in Brazil is the Usercontrol. Behold the description of the components here.
– Sidon