| Olivita AS | Wholesale & retail | 2002 |
| Olli Invest AS | Financial services | 2005 |
| Olsen Holding AS | Real estate | 1997 |
| Om Measuring Tools AS | Administrative & support | 2009 |
| Omhu Nord AS | Real estate | 2024 |
| Ommerstua SA | Real estate | 2025 |
| Ommøblert AS | Wholesale & retail | 2023 |
| Onda Group AS | Professional & scientific | 2023 |
| Onegen AS | Real estate | 2023 |
| Onico AS | Professional & scientific | 2001 |
| Onkovit AS | Health & social care | 2014 |
| Only Group AS | Administrative & support | 2022 |
| Only Invest AS | Administrative & support | 2020 |
| Opalia Tannklinikk Tromsø AS | Health & social care | 2014 |
| Ope Invest AS | | 2025 |
| Open Grains AS | Information & communication | 2026 |
| Optik Jekta AS | Wholesale & retail | 1997 |
| Optik Nord Troms AS | Wholesale & retail | 1997 |
| Optik Spesialbutikken AS | Wholesale & retail | 2016 |
| Optik Spesialbutikken I Nord AS | Wholesale & retail | 2025 |
| Optiker Stein-Tore Hansen AS | Wholesale & retail | 2004 |
| Optikus Magnus Jacobsen AS | Wholesale & retail | 1994 |
| Optimal Hund AS | Other services | 2017 |
| Oracel Holding AS | Real estate | 2022 |
| Oracel Surge AS | Real estate | 2023 |
| Oratory AS | Education | 2024 |
| Orbital Ans | Information & communication | 2002 |
| Orbital Networks AS | Information & communication | 2016 |
| Orca Labs AS | Information & communication | 2018 |
| Orcan Holding AS | | 2026 |
| Ordna AS | Information & communication | 2026 |
| Organisasjonspsykologene Skare AS | Professional & scientific | 2016 |
| Orient Internasjonale Matbutikk AS | Wholesale & retail | 2021 |
| Original Film AS | Information & communication | 1997 |
| Ortoped Hanne Rasmussen AS | Health & social care | 2025 |
| Ortoped Og Idrettslege Mette Andersen AS | Health & social care | 2023 |
| Osbourne AS | Administrative & support | 2024 |
| Otb Construction AS | Construction | 2020 |
| Ottesen Maskin & Transport AS | Construction | 2008 |
| Ousland Eiendom AS | Real estate | 2025 |
| Ousland Invest AS | Real estate | 2025 |
| Outdoor Cabins AS | Wholesale & retail | 2018 |
| OV10A AS | Real estate | 2025 |
| Overvaag AS | Financial services | 2005 |
| Ownthat AS | Real estate | 2016 |
| Oya Holding AS | | 2025 |
| Pact AS | Professional & scientific | 2020 |
| Pago AS | Real estate | 2018 |
| Paktolos Holding AS | Wholesale & retail | 2017 |
| Palarctic Productions AS | Information & communication | 2025 |
| Palmi Rosendahl AS | Information & communication | 2026 |
| Palouse AS | Administrative & support | 2004 |
| Pamo Invest AS | Wholesale & retail | 2015 |
| Pan Prosjekt AS | Construction | 2021 |
| Panama Papers AS | Information & communication | 2019 |
| Pandion Capital AS | | 2025 |
| Panorama Business Support AS | Professional & scientific | 2023 |
| Panzerbjörn AS | Arts & recreation | 2013 |
| Paramount AS | Hospitality | 2024 |
| Paramount Holding AS | | 2025 |
| Parrilla Retreats AS | Education | 2024 |
| Partnerconsult AS | Professional & scientific | 2016 |
| Partrederiet Kaswig Da | Agriculture & fishing | 2011 |
| Pashbame Invest AS | | 2022 |
| Pastafabrikken AS | Hospitality | 2009 |
| Pathway Consulting AS | Health & social care | 2024 |
| Pathway Consulting Holding AS | Health & social care | 2024 |
| Paul T Aandahl AS | | 2024 |
| PC Nord AS | Other services | 2024 |
| PCP Eiendomsinvest AS | Real estate | 2025 |
| Peab Asfalt Norge AS | Manufacturing | 2009 |
| Peab Bygg AS | Construction | 1987 |
| Peab Norge Holding AS | Construction | 2017 |
| Peab Utbygging AS | Real estate | 2015 |
| Peak Norway AS | Professional & scientific | 2024 |
| Peco Eiendom AS | Real estate | 2005 |
| Pedago AS | Hospitality | 1992 |
| Pedersen AS | | 2025 |
| Pedersen Bakeri AS | Manufacturing | 2013 |
| Pedersen Brøyting AS | Construction | 2000 |
| Pedersen Capital AS | | 2025 |
| Pedlar AS | Wholesale & retail | 2025 |
| Pekma Holding AS | | 2020 |
| Pekog Invest AS | Real estate | 2005 |
| Pelemo AS | | 2025 |
| Pellerin AS | Real estate | 2020 |
| Pellerin Holding AS | Real estate | 1876 |
| Pellerinbryggene AS | Real estate | 2022 |
| Pelly Workwear Tromsø AS | Wholesale & retail | 2023 |
| Pelto Invest AS | Health & social care | 2015 |
| Pendulum AS | Health & social care | 2016 |
| Pendulum Balanse AS | Health & social care | 2024 |
| Peptide Patents AS | Administrative & support | 2019 |
| Per CHR. Gundersen AS | Health & social care | 2013 |
| Per Molund Invest AS | Wholesale & retail | 2005 |
| Peran Invest AS | | 2025 |
| Perfect Temperature Group AS | Construction | 2017 |
| Perfekt Renseri AS | Real estate | 2007 |
| Perles Design AS | Arts & recreation | 2022 |
| Pero Eiendom AS | Real estate | 2000 |