All companies have to provide a list of owners each year to our tax agency Skatteetaten ("IRS"). The data isn't exactly publicly available AFAIK, but anyone can ask for access.
It lists owners, but as you can see it's mostly "Holding Companies". However, pressing "Indirekte eierskap og eiere" ("Indirect ownerships") one can see the true companies or persons behind those.
This is a company doing extra stuff with the data, and providing some of it directly online. Here's a lookup of the company I work for: https://proff.no/aksjon%C3%A6rer/bedrift/oda-group-holding-a...
It lists owners, but as you can see it's mostly "Holding Companies". However, pressing "Indirekte eierskap og eiere" ("Indirect ownerships") one can see the true companies or persons behind those.