| Northeast AS | Manufacturing | 2024 |
| Norwegian Aesthetics AS | Wholesale & retail | 2024 |
| Nostalgic Records AS | Information & communication | 2026 |
| Noti AS | Real estate | 2019 |
| Nova Spektrum AS | Administrative & support | 2018 |
| Novara AS | Health & social care | 2025 |
| Novateur Design Og Kommunikasjon AS | Professional & scientific | 2016 |
| Novo Gruppen AS | Health & social care | 2018 |
| Noyb Invest AS | | 2021 |
| Nsu Nordic Service Union AS | Construction | 2016 |
| Nurdent Lillestrøm Tannlegesenter AS | Health & social care | 2021 |
| Nursing Europe AS | Administrative & support | 2015 |
| Nuvinno AS | Information & communication | 2024 |
| Nuvinno Group AS | Information & communication | 2025 |
| Nyberg Consulting AS | Professional & scientific | 2025 |
| Nydahl Engineering AS | Wholesale & retail | 2018 |
| Nye Aziz Invest AS | | 2026 |
| Nye Industrivegen 72 AS | Real estate | 2022 |
| Nye Lillestrøm Øre Nese Hals AS | Health & social care | 2021 |
| Nye Martins AS | Hospitality | 2016 |
| Nyevo AS | Information & communication | 2019 |
| Nygårdsjordet AS | Real estate | 2013 |
| Nøkkeleiendom AS | Real estate | 1992 |
| O Johansen & Sønner AS | Wholesale & retail | 1978 |
| O Syversens Eiendommer AS | Real estate | 1972 |
| O.A.H Holding AS | | 2026 |
| Ocean Astoria Investment Nuf | Real estate | 2006 |
| Ocean Harvest AS | Wholesale & retail | 2017 |
| Odalsgata 25 AS | Real estate | 2009 |
| Odalsgata 29 AS | Real estate | 2009 |
| Odnes Holding AS | Wholesale & retail | 1991 |
| Oeb Holding AS | Real estate | 2022 |
| Oeb Utleie AS | Administrative & support | 2022 |
| Ok Agentur AS | Other services | 2011 |
| Okam AS | Information & communication | 2020 |
| Okam Gruppen AS | Information & communication | 2022 |
| Okaya AS | Wholesale & retail | 2025 |
| Olaisen Gruppen AS | Manufacturing | 2012 |
| Oleda AS | Real estate | 2004 |
| Onics Norway AS | Wholesale & retail | 2016 |
| Opax AS | Information & communication | 2005 |
| Opedia Holding AS | Administrative & support | 2008 |
| Oppsal Multiservice AS | Administrative & support | 2019 |
| Opticus Øyeklinikk AS | Health & social care | 2024 |
| Optima Forvaltning AS | Real estate | 1996 |
| Oriented Accounting AS | Professional & scientific | 2025 |
| Orizuru AS | Professional & scientific | 2019 |
| Oslo Autohandel AS | Wholesale & retail | 2025 |
| Oslo Blåseisolering AS | Construction | 2025 |
| Oslo Og Romerike Rørleggerbedrift AS | Construction | 2021 |
| Oslo Regnskapssenter AS | Administrative & support | 2017 |
| Oslotaxi 1 AS | Transport & logistics | 2025 |
| Osprey Event AS | Arts & recreation | 2013 |
| Otiumpluss Nyli Bolig AS | Real estate | 2025 |
| Otiumpluss Nyli Næring AS | Real estate | 2025 |
| Otiumpluss Vingnes Bolig AS | Real estate | 2026 |
| Otiumpluss Vingnes Næring AS | Real estate | 2026 |
| Overlat AS | Administrative & support | 2026 |
| Ovg 8 AS | Real estate | 2023 |
| P-Plassmegleren AS | Real estate | 2011 |
| P.Berg Invest AS | Real estate | 2005 |
| P51 Holding AS | | 2026 |
| Padvise AS | | 2021 |
| Palle Sørensen Transport AS | Transport & logistics | 2005 |
| Pandhys Norge AS | Wholesale & retail | 2019 |
| Pandion Holding AS | | 2026 |
| Panorama Invest AS | Real estate | 1987 |
| Paper Supply Services AS | Wholesale & retail | 2006 |
| Paperbox AS | Wholesale & retail | 2001 |
| Papillon AS | Real estate | 2015 |
| Paragraf Eiendom AS | Real estate | 1998 |
| Parkalléen Næring AS | Real estate | 2017 |
| Parkalléen Parkering AS | Transport & logistics | 2017 |
| Parken Og Nygård Ans | Other services | 1991 |
| Parus AS | Professional & scientific | 2016 |
| Passasjen Næring 2 AS | Real estate | 2022 |
| Passasjen Næring 3 AS | Real estate | 2022 |
| Passasjen Næring 4 AS | Real estate | 2022 |
| Patri Invest & Trading AS | Professional & scientific | 1991 |
| Payrun AS | Information & communication | 2016 |
| Pearly AS | Wholesale & retail | 2025 |
| Peik Capital AS | | 2025 |
| Pensjonskonto AS | Professional & scientific | 2020 |
| Per Arntzen Trading AS | Wholesale & retail | 2002 |
| Periscopify AS | Information & communication | 2025 |
| Pernille AS | Wholesale & retail | 1961 |
| Pernod Ricard Norway AS | Wholesale & retail | 1995 |
| Pertra AS | Wholesale & retail | 2020 |
| Pescamar Holding AS | Agriculture & fishing | 2018 |
| Pharmacosmos Norway AS | Wholesale & retail | 2011 |
| Philip Fossum Skjølberg AS | | 2021 |
| Philo AS | Information & communication | 2022 |
| Photoshop AS | Professional & scientific | 1998 |
| Piece of Mind AS | Real estate | 2025 |
| Pier Holding AS | | 2025 |
| Piermont Solutions AS | Information & communication | 2024 |
| Pilates Zone Lillestrøm Ltd Nuf | Education | 2016 |
| Pilestredet Eiendom AS | Real estate | 2006 |
| Pineconsultant Nuf | Professional & scientific | 2011 |
| Pink by Utseende.No Oslo AS | Wholesale & retail | 2023 |