| Orator Team AS | Oslo | 2012 |
| Oratory AS | Tromsø | 2024 |
| Ordlandia AS | Oslo | 2026 |
| Ordrett Ordkontor Ans | Oslo | 2004 |
| Orheim Invest AS | Stårheim | 2018 |
| Orion Mma Academy AS | Tønsberg | 2022 |
| Orkdal Trafikkskole AS | Orkanger | 2025 |
| Orkla Utleie AS | Løkken Verk | 2026 |
| Orkland Trafikkskole AS | Fannrem | 2017 |
| Ormaskogen Barnehage SA | Sandnes | 2002 |
| Orphan Medical AS | Oslo | 2021 |
| Orrestien Barnehage AS | Vinterbro | 2009 |
| Os / Byens Trafikkskole AS | Os | 1994 |
| Os Consulting AS | Stavanger | 2005 |
| Osanstua Barnehage AS | Svolvær | 2018 |
| Osc 2 AS | Snarøya | 2022 |
| Ose Fitness AS | Kristiansand S | 2014 |
| Oslo Brannvern Og Sikring Ans | Lysaker | 2002 |
| Oslo College of Managment Da | Lørenskog | 2013 |
| Oslo Dance Seminar Da | Oppegård | 2023 |
| Oslo Flight Academy AS | Stabekk | 2020 |
| Oslo Fotokunstskole AS | Oslo | 2005 |
| Oslo International Academy Oia AS | Oslo | 2022 |
| Oslo International Piano Studio AS | Oslo | 2023 |
| Oslo Iyengar Yoga - Mandala Yoga AS | Oslo | 2016 |
| Oslo Keeperskole AS | Oslo | 2016 |
| Oslo Keramikkverksted AS | Oslo | 2022 |
| Oslo Keramikkverksted Avd Majorstua AS | Oslo | 2024 |
| Oslo Kulturfabrikk AS | Østerås | 2017 |
| Oslo Kvinnehelsesenter AS | Oslo | 2016 |
| Oslo Language School AS | Oslo | 2018 |
| Oslo Movement Ans | Oslo | 2017 |
| Oslo Negler AS | Oslo | 2018 |
| Oslo NF AS | Oslo | 2022 |
| Oslo Nye Fagskole AS | Oslo | 2020 |
| Oslo Nye Høyskole AS | Oslo | 2007 |
| Oslo Parkour Park AS | Oslo | 2019 |
| Oslo Performance Training | Larvik | 2013 |
| Oslo Pianoskole AS | Oslo | 2023 |
| Oslo Private Gymnasium AS | Oslo | 1989 |
| Oslo Private Musikkskole AS | Oslo | 2012 |
| Oslo PT Studio AS | Oslo | 2018 |
| Oslo Rock School AS | Jar | 2016 |
| Oslo Sea Experience AS | Oslo | 2024 |
| Oslo Seilskole AS | Oslo | 2007 |
| Oslo Syd Trafikkskole Holmlia AS | Oslo | 2018 |
| Oslo Team Trafikkopplæring AS | Oslo | 2013 |
| Oslo Team Trafikkskole AS | Oslo | 2012 |
| Oslo Trafikkskole AS | Oslo | 2015 |
| Oslo Vest Trafikkskole AS | Oslo | 2012 |
| Oslo Vindtunelldrift AS | Lørenskog | 2023 |
| Oslo Wine School AS | Oslo | 2012 |
| Oslo Yoga AS | Oslo | 2014 |
| Oslo Øst Trafikkskole AS | Oslo | 2023 |
| Oslofjorden Dykkersenter AS | Vollen | 2013 |
| Osm Aviation Academy AS | Arendal | 2017 |
| Osm Aviation Academy Holding AS | Arendal | 2017 |
| Osm Aviation Technical Training AS | Bardufoss | 2019 |
| Osol Språkkurs AS | Oslo | 2025 |
| Ossihuset AS | Stavanger | 2026 |
| Ostereidet Fus Barnehage AS | Ostereidet | 2018 |
| Osterøy Gårds Og Friluftsbarnehage AS | Valestrandsfossen | 2004 |
| Osterøy Mindfulness Hartveit | Valestrandsfossen | 2013 |
| Ostrøm Kurs Og Utvikling AS | Lunde | 2015 |
| Otd Akademiet AS | Frogner | 2014 |
| Ottershagen Gardsbarnehage AS | Rena | 2004 |
| Otterstrom Racing AS | Hokksund | 2023 |
| Ottersøy Barnehage SA | Ottersøy | 1976 |
| Otto Essentials Oils AS | Skarnes | 2021 |
| Otto Fredriksson AS | Lillehammer | 2026 |
| Otto Treider Idrett AS | Oslo | 2015 |
| Otto Treider Private Gymnas AS | Oslo | 1975 |
| OV18 Kultur AS | Steinkjer | 2022 |
| Overhalla Montessoriskole SA | Overhalla | 2013 |
| Overlevelseskompaniet AS | Fornebu | 2025 |
| Overn Trafikkskole AS | Slattum | 2024 |
| Overskudd Opplæring AS | Hosle | 2004 |
| Ovt AS | Oslo | 2018 |
| Ower Trafikkskole AS | Skedsmokorset | 2024 |
| Oydawi AS | Levanger | 2020 |
| Oz Consulting AS | Leinøy | 2011 |
| Ozonic AS | Ottestad | 2018 |
| Ozsea AS | Bergen | 2017 |
| P.G Trafikkopplæring AS | Namsos | 2017 |
| Paal Aagaard Svømmekonsult AS | Trondheim | 2014 |
| Pace Pilot AS | Rygge | 2024 |
| Padel Senter Fredrikstad AS | Fredrikstad | 2023 |
| Padel Sør AS | Kristiansand S | 2019 |
| Padlegleden AS | Høvåg | 2023 |
| Padletur AS | Trondheim | 2018 |
| Pain Freedom AS | Oslo | 2022 |
| Painfreeu AS | Straume | 2015 |
| Painfreeu Technology AS | Knarrevik | 2023 |
| Paint on Pots Sentrum AS | Oslo | 2024 |
| Paint on Pots Stavanger AS | Oslo | 2024 |
| Palatin AS | Oslo | 2013 |
| Palatin Holding AS | Oslo | 2013 |
| Paletten Familiebarnehage AS | Skjeberg | 2022 |
| Palisade Europe UK Ltd | West Drayton-Middlesex Ub7 7Pn | 2010 |
| Palmqvist AS | Oslo | 1992 |