| Hystad Eiendomsforvaltning AS | Real estate | 2007 |
| Hystad Østre AS | Agriculture & fishing | 2025 |
| Hystadveien 24 AS | Real estate | 2022 |
| Hystadveien 246 AS | Real estate | 2024 |
| Hystadveien 3 AS | Real estate | 2021 |
| Hystadveien AS | Real estate | 1995 |
| Hystadveien Holding AS | Real estate | 2021 |
| Hystadåsen AS | Real estate | 2019 |
| Hytteavisen AS | Information & communication | 2016 |
| Hyttemessen AS | Administrative & support | 2013 |
| Hyttetorget AS | Wholesale & retail | 1992 |
| Hågan Holding AS | Real estate | 2011 |
| Hågasletta 1 AS | Real estate | 2025 |
| Hågasletta 10 AS | Real estate | 2014 |
| Hågasletta 2 AS | Real estate | 2008 |
| Hågasletta 6-8 AS | Real estate | 2012 |
| Hågasletta 7 AS | Real estate | 2026 |
| Hågasletta Holding AS | Wholesale & retail | 2020 |
| Hågen Bygg AS | Construction | 2023 |
| Håkonsen Tømrer Service AS | Construction | 2026 |
| Hålogaland Plankontor AS | Professional & scientific | 1976 |
| Håndverkeren Kaffebrenneri AS | Hospitality | 2012 |
| Hårfin AS | Other services | 2008 |
| Hårgalleriet Sandefjord AS | Other services | 2023 |
| Hårteigen AS | Real estate | 1998 |
| Håsv Drift SA | Water & waste | 2023 |
| Høg Invest AS | Real estate | 1996 |
| Høgenhall Barnehage SA | Education | 1992 |
| Høgseth Prosjekt AS | Professional & scientific | 2014 |
| Høgtor AS | Professional & scientific | 2006 |
| Høgåsen Eiendomsselskap AS | Real estate | 1984 |
| Høikaas AS | Real estate | 2022 |
| Høyer Sandefjord AS | Wholesale & retail | 2020 |
| I-Group AS | Wholesale & retail | 2010 |
| I-Store AS | Professional & scientific | 2026 |
| I-Veien 83 AS | | 2026 |
| Iak Kapital AS | Construction | 2023 |
| Iak Social Studios AS | Arts & recreation | 2024 |
| Ib-Holding AS | Real estate | 2018 |
| Ibis Holding AS | Professional & scientific | 2018 |
| Ibt AS | Real estate | 2023 |
| Ican AS | Wholesale & retail | 2009 |
| Ican Trend AS | Wholesale & retail | 2009 |
| Ican Trend Da | Wholesale & retail | 2002 |
| Ich AS | Wholesale & retail | 2019 |
| Ieagle Invest AS | Real estate | 2017 |
| Ignite Capital AS | Information & communication | 2022 |
| Ignite Capital Fund I AS | Financial services | 2022 |
| Ignite Capital I AS | | 2022 |
| Ignite Capital Management AS | Financial services | 2022 |
| Ihud AS | Health & social care | 2018 |
| Ikde Holding AS | | 2017 |
| Iki Asset Management AS | | 2023 |
| Il Rengjøring AS | Administrative & support | 2017 |
| Im Ressurs AS | Education | 2007 |
| Ima Green Holding AS | | 2025 |
| Imap AS | Administrative & support | 2006 |
| Imap Eiendom AS | Real estate | 2007 |
| Imap Norge AS | Professional & scientific | 2001 |
| Impensum Invest AS | | 2025 |
| In Numeris AS | Professional & scientific | 2025 |
| In Sync AS | Information & communication | 2018 |
| Incubeat AS | Real estate | 2007 |
| Incubeat Estate AS | Real estate | 2021 |
| Incubeat Xpnd AS | Information & communication | 2021 |
| Industri Mekanikk AS | Administrative & support | 2001 |
| Industriveien 89 AS | Real estate | 2005 |
| Industriveien NR 85 AS | Real estate | 2022 |
| Infodesk AS | Information & communication | 2019 |
| INFOMEDIA SANDEFJORD DA Roy Pedersen og Rune Brynhildsen | Manufacturing | 1990 |
| Infostation AS | Information & communication | 2000 |
| Infra Towers AS | Wholesale & retail | 2012 |
| Ing. Quamme AS | Professional & scientific | 2016 |
| Inge Kronstad AS | | 2023 |
| Ingeniør Bjørn Tyvold AS | | 2005 |
| Ingås AS | Financial services | 2005 |
| Inhouse AS | Arts & recreation | 2018 |
| Initiate AS | Information & communication | 2007 |
| Innafor Arkitektur & Design AS | Professional & scientific | 2016 |
| Innowin AS | Professional & scientific | 2013 |
| Innstrand AS | Health & social care | 2018 |
| Inside IT AS | Information & communication | 2024 |
| Intectus AS | Financial services | 2013 |
| Intek AS | Professional & scientific | 1988 |
| International Business to Business AS | Professional & scientific | 1995 |
| International Mission Board | Other services | 2014 |
| Intertek Certification AS | Professional & scientific | 2000 |
| Intertek Inspection Services Scandinavia AS | Professional & scientific | 2000 |
| Intexskandia AS | Wholesale & retail | 1989 |
| Into Design AS | Professional & scientific | 2007 |
| Intrepido AS | Wholesale & retail | 2017 |
| Intuition AS | Manufacturing | 2018 |
| Invaria AS | Education | 2026 |
| Inventia Holding AS | | 2022 |
| Investbolig AS | Construction | 2025 |
| Investbygg AS | Construction | 2025 |
| Investeq AS | Information & communication | 2014 |
| Investforvaltning AS | Real estate | 2005 |
| Investor's Center AS | Professional & scientific | 2022 |
| Involved Consulting AS | Professional & scientific | 2024 |