Hello @Leighton Birchard
Welcome to Microsoft QnA!
Yes the service is named Conditonal Access and you need at least Premium P1 on your Tenant
Licenses of E3 and E5 ( Microsoft E3 and E5 contain that )
https://cloudcompanyapps.com/2019/04/18/block-users-by-location-in-azure-o365/
I hope this helps!
Kindly mark the answer as Accepted and Upvote in case it helped!
Regards