A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z | 1
| OBOS (5) | Ocean Installer AS (16) |
| Ocean Rig (8) | Oceaneering (9) |
| Oceaneering AS (18) | Oceaneering International (8) |
| Odfjell Drilling AS (6) | On Off Bemanning as (6) |
| OneERP Ltd (6) | Ontime Logistics (4) |
| ONTOS (4) | Opera Software (15) |
| Oppegård Kommune (16) | Optimera AS (4) |
| Orcus Hordaland (4) | Orcus Rogaland (10) |
| Orion Group (34) | Orkdal kommune (5) |
| Orkla ASA Bakers (5) | Orkla ASA Stabburet (5) |
| Ørsta Kommune (10) | Oslo universitetssykehus HF (18) |
| OSM People (5) | Osterreichische Post AG - Unternehmenszentrale (7) |
| Overhalla Kommune (4) | Øvre Eiker Kommune (5) |
| OXX AS (5) | Oyatel (5) |
| Oygarden kommune (5) |