How to get the organization (tenant) id from user profile using the Microsoft Graph API

This seems to work

GET https://graph.microsoft.com/v1.0/organization 

The id property is the Tenant Id

Grahp Explorer link

Now this may not be using the graph API directly , but makes it extremely simple to obtain the tenant id of an organization. Just do a GET to "https://login.microsoftonline.com/{yourdomainname}/.well-known/openid-configuration". The structure returned will have the tenant id. Try this url for example in your browser: https://login.microsoftonline.com/microsoft.com/.well-known/openid-configuration.

If nothing else works, you can decode the access token and get the tid claim. That is the id for the Azure AD tenant.

You can find the documentation for the claims in tokens from here: https://docs.microsoft.com/en-us/azure/active-directory/develop/active-directory-token-and-claims

For example, here is what it says for tid:

An immutable, non-reusable identifier that identifies the directory tenant that issued the token. You can use this value to access tenant-specific directory resources in a multi-tenant application. For example, you can use this value to identify the tenant in a call to the Graph API.