| Irg 99 AS | Real estate | 2002 |
| Isa Renhold AS | Administrative & support | 2020 |
| Isbjørn Holding AS | Financial services | 2006 |
| Isewa AS | Professional & scientific | 2025 |
| Isinf AS | Financial services | 2017 |
| Isoblikk Eiendom AS | Real estate | 1997 |
| Isomar AS | Transport & logistics | 1993 |
| Isotank AS | Administrative & support | 2026 |
| Ispirit AS | Education | 2017 |
| Issy AS | Administrative & support | 2017 |
| Isverk Holding AS | Administrative & support | 2023 |
| Italmarin AS | Wholesale & retail | 2012 |
| Itc Nordic AS | Professional & scientific | 2005 |
| Ivar Olsen Consulting AS | Construction | 2015 |
| Ivar Tanum Entreprenør AS | Construction | 2004 |
| Ivar Tanum Maskinutleie AS | Administrative & support | 1990 |
| Ivarsson Holding AS | | 2025 |
| Ivda AS | Real estate | 2010 |
| Ivilde AS | Financial services | 2005 |
| Iwi AS | | 2024 |
| Izzi AS | Construction | 2005 |
| J & F MURERSERVICE Johansen & Friise ANS | Construction | 1994 |
| J & J Association Ans | Wholesale & retail | 1989 |
| J Karoliussen Bygg KB | Construction | 1996 |
| J&J Holding AS | | 2025 |
| J&S Service AS | Hospitality | 2015 |
| J. Øvland Holding AS | | 2021 |
| J.Botilsrud Holding AS | Financial services | 2011 |
| J.O Benjaminsen Holding AS | | 2025 |
| J/S Serviceteam AS | Other services | 2012 |
| Ja Svendsen Holding AS | Information & communication | 2019 |
| Jaan Invest AS | | 2025 |
| Jabror AS | Professional & scientific | 2018 |
| Jag AS | Real estate | 2005 |
| Jag Holding AS | Real estate | 2008 |
| Jahic Invest AS | Construction | 2012 |
| Jaki AS | Real estate | 2008 |
| Jakri AS | Wholesale & retail | 1996 |
| Jaktdepotet AS | Wholesale & retail | 2003 |
| Jaktklær AS | Wholesale & retail | 2012 |
| Jakupovic Holding AS | Real estate | 2025 |
| Jalvin AS | Transport & logistics | 2021 |
| Jan-Roger Gundersen AS | Other services | 2005 |
| Jana Brodszki | Health & social care | 2013 |
| Jani Invest AS | Financial services | 2005 |
| Jarle Brunvoll AS | Professional & scientific | 2019 |
| Jarle Og Patrick Holding AS | | 2024 |
| Jarlsbergsenteret AS | Real estate | 2025 |
| Jarlsbergveien 3 AS | Real estate | 2022 |
| Jarnang Invest AS | Wholesale & retail | 2012 |
| Jas IT Consulting AS | Information & communication | 2019 |
| Jasmin Kompetanse AS | Education | 2023 |
| Jason Engineering AS | Manufacturing | 2023 |
| Jass Eiendom AS | Real estate | 2026 |
| Jass Nord AS | Professional & scientific | 2006 |
| JCC Invest AS | | 2015 |
| JCK Servicetjenester AS | Administrative & support | 2023 |
| Jckeiendom AS | Real estate | 2023 |
| Jcml AS | Professional & scientific | 2024 |
| JD Juridiske Dokumenter AS | Professional & scientific | 2025 |
| Je Qa/Qc-Inspection & Consulting AS | | 2007 |
| Je Qa/Qc-Services AS | Professional & scientific | 2006 |
| Jebo Servicesystemer AS | Construction | 2015 |
| Jegertunet Holding AS | Hospitality | 2015 |
| Jemisco Holding AS | | 2026 |
| Jenga AS | Real estate | 2021 |
| Jensens Bil-Service Da | Other services | 2001 |
| Jensenvarme Holding AS | Real estate | 2022 |
| Jensvoll Næringspark AS | Real estate | 2009 |
| Jensvollveien 26 AS | Real estate | 2014 |
| Jet JR. Invest AS | Real estate | 2014 |
| JG Maskin Utleie AS | Administrative & support | 2022 |
| Jgruppen AS | Administrative & support | 2017 |
| JHQ AS | Financial services | 2005 |
| JJ Invest AS | Construction | 2005 |
| JK Interiørsnekkeren AS | Manufacturing | 2025 |
| JLJ Management AS | Financial services | 2015 |
| JLJ-1 AS | Professional & scientific | 2022 |
| JLT AS | Real estate | 2019 |
| Jma Invest AS | Financial services | 2017 |
| Jmcon AS | Professional & scientific | 2022 |
| JMG Management AS | Real estate | 2016 |
| Jmi Byggteam AS | Construction | 2023 |
| JMS Investment AS | Wholesale & retail | 2021 |
| JN Utleie AS | Real estate | 2019 |
| Jo-Topp Holding AS | Wholesale & retail | 2021 |
| Joahe AS | Wholesale & retail | 2014 |
| Joahe Consulting AS | Information & communication | 2024 |
| Jobcontrol AS | Professional & scientific | 1998 |
| Jobnest AS | Information & communication | 2020 |
| Jodel Invest AS | Real estate | 1998 |
| Joe Bygg AS | Construction | 2022 |
| Joe Group AS | Construction | 2022 |
| Joggen Sport Profil AS | Wholesale & retail | 2010 |
| Johan Halvorsen Musikkfest SA | Administrative & support | 2011 |
| John Erik Nilsen AS | Professional & scientific | 2006 |
| John Munkhaugen AS | Real estate | 1990 |
| Johnsen Invest AS | Real estate | 1999 |
| Joho Investering AS | Financial services | 2014 |
| Johs. Rasmussen Transport | Transport & logistics | 2013 |