| Jan Fredrik Newco AS | | 2021 |
| Jan Gunnar Sørbø AS | | 2025 |
| Jan Investment Holding AS | Financial services | 1997 |
| Jan Jahren AS | | 2026 |
| Jan Kåre Midthjell Holding AS | Real estate | 2015 |
| Jan Lillehagen AS | | 1986 |
| Jan M Rød AS | Transport & logistics | 1982 |
| Jan Marheim Invest AS | Financial services | 2005 |
| Jan Martin Johnsen AS | Arts & recreation | 2022 |
| Jan Meling Holding AS | Information & communication | 2011 |
| Jan Mortensen Holding AS | | 2020 |
| Jan Og Jo Elektro AS | Construction | 2000 |
| Jan Olav Stokke Invest AS | Wholesale & retail | 2005 |
| Jan Olav Sørdal AS | Health & social care | 2012 |
| Jan Ottesen Consulting AS | Professional & scientific | 2025 |
| Jan P Harto AS | Professional & scientific | 1989 |
| Jan P Harto Holding AS | Professional & scientific | 2018 |
| Jan Petter Knutsen Invest AS | Health & social care | 2019 |
| Jan Robert Kvam AS | Administrative & support | 2014 |
| Jan Rygh AS | Information & communication | 2012 |
| Jan Thomas Studio AS | Other services | 2007 |
| Jan Thomas Studio Group AS | Other services | 2022 |
| Jan Vadder AS | Financial services | 2005 |
| Jan Øyvind Larsen Invest AS | | 2005 |
| Jan-Eirik Hansen AS | Professional & scientific | 2007 |
| Jan-Erik Ryd | Construction | 2001 |
| Jan-Fredrik Borge AS | Professional & scientific | 1986 |
| Jana Holding AS | | 2025 |
| Jana Renhold AS | Administrative & support | 2025 |
| Janaflaten Næringsbygg AS | Real estate | 2016 |
| Janca Invest AS | | 2019 |
| Janda AS | | 2022 |
| Jandersen Holding AS | | 2020 |
| Janeri AS | Financial services | 2018 |
| Janest AS | Health & social care | 2022 |
| Jang AS | Financial services | 2005 |
| Jangor Investment Limited | Wholesale & retail | 2022 |
| Jani Holding Oslo AS | | 2026 |
| Jani Teck Invest AS | | 2026 |
| Janicki & Co Byggservice Da | Construction | 2006 |
| Janicki Bygg Da | Construction | 2006 |
| Janin Holding AS | | 2024 |
| Janine Wino AS | Education | 2024 |
| Janita Invest AS | Real estate | 2017 |
| Janix Ikt AS | Transport & logistics | 2016 |
| Janjua Holdings AS | Information & communication | 2022 |
| Jankenicer AS | | 2022 |
| Janna Beauty AS | Other services | 2024 |
| Janna Brattlis Holding AS | Education | 2016 |
| Janne B Design AS | Professional & scientific | 2018 |
| Janne Formoe AS | Arts & recreation | 2021 |
| Janne Olsson Grav Och Planering | Construction | 1997 |
| Jannicke Grung AS | | 2020 |
| Jannicke S AS | Real estate | 2016 |
| Jannik AS | Wholesale & retail | 2024 |
| Jans Team AS | Wholesale & retail | 2025 |
| Jansberg Forretning AS | Real estate | 1997 |
| Jansen Investering AS | Professional & scientific | 2018 |
| Jansen Management Consulting AS | Professional & scientific | 2024 |
| Jansen Plateproduksjon AS | Information & communication | 2014 |
| Jansen Prosjekt AS | Professional & scientific | 2021 |
| Jansen Publishing AS | Professional & scientific | 2019 |
| Janssen-Cilag AS | Wholesale & retail | 1995 |
| Jantb Holding AS | | 2020 |
| Janteloppet AS | Professional & scientific | 2022 |
| Jantjo Invest AS | Real estate | 2007 |
| JANUAR09 Invest AS | Real estate | 2019 |
| Japco AS | Professional & scientific | 2011 |
| Japo Henry AS | Real estate | 2014 |
| Japo Sushi Frogner AS | Hospitality | 2016 |
| Japo Sushi Skøyen AS | Hospitality | 2016 |
| Japo Sushi Sognsvann AS | Hospitality | 2016 |
| Jappe Ippes Vei 6 -10 AS | Real estate | 2020 |
| Jaqueline Da | Arts & recreation | 2006 |
| Jar Elektro AS | Construction | 2018 |
| Jar Holding I AS | | 2025 |
| JAR4 AS | Wholesale & retail | 2019 |
| Jara Shipping Og Trading AS | Transport & logistics | 2000 |
| Jarah Invest AS | Real estate | 2005 |
| JARBAKK1 AS | Professional & scientific | 2005 |
| Jarbeaux Holding AS | Wholesale & retail | 2012 |
| Jarbeaux Sport AS | Wholesale & retail | 2012 |
| Jarbø & Co. AS | | 2023 |
| Jardis Invest AS | Real estate | 2020 |
| Jareid Holding AS | | 2022 |
| Jarek AS | | 2018 |
| Jaren Heller AS | Real estate | 1974 |
| Jaren Utvikling AS | Real estate | 2021 |
| Jarhuset Eiendom AS | Real estate | 2009 |
| Jarib Invest AS | Real estate | 2005 |
| Jarisa Holding AS | | 2024 |
| Jarl Holding AS | Financial services | 2005 |
| Jarla Invest AS | | 2023 |
| Jarle Hovland Holding AS | | 2021 |
| Jarlez AS | Financial services | 2007 |
| Jarlsbo Invest AS | Real estate | 2018 |
| Jarlsborg Holding AS | | 2025 |
| Jarlsborgveien 3 (Nord) AS | Real estate | 2011 |
| Jarltronikk AS | Wholesale & retail | 2017 |
| Jarmann 2 AS | Hospitality | 2018 |