| Siem Kapital AS | Transport & logistics | 1993 |
| Siem Offshore Ahts AS | Transport & logistics | 2022 |
| Siem Offshore AS | Transport & logistics | 2024 |
| Siem Offshore Opco AS | Mining & quarrying | 2024 |
| Siem Offshore Oscv AS | Transport & logistics | 2024 |
| Siem Offshore PSV AS | Transport & logistics | 2024 |
| Siem Offshore Supply AS | Transport & logistics | 2024 |
| Siem Shipowning I Norway AS | Transport & logistics | 2011 |
| Siem Shipping Norway AS | Transport & logistics | 1997 |
| Sifam AS | Real estate | 2006 |
| Sifi Invest AS | Real estate | 2024 |
| Sigma Capital AS | Professional & scientific | 2012 |
| Sigma Drilling AS | Manufacturing | 2007 |
| Sigma Valmon AS | Wholesale & retail | 2024 |
| Sigo Invest AS | Professional & scientific | 2008 |
| Sigurd B. AS | Real estate | 2007 |
| Sigurd Drangsholt Eiendom AS | Real estate | 2004 |
| Sigurd H Frigstad AS | Construction | 1979 |
| Sigurd Nyborg Holding AS | | 2022 |
| Sijaas AS | Real estate | 2020 |
| Sijada AS | Real estate | 2005 |
| Sika Fidjeland AS | | 2017 |
| Sildeholmen AS | Financial services | 2016 |
| Silent Sea AS | Wholesale & retail | 2021 |
| Sille Marie AS | Agriculture & fishing | 1991 |
| Silleholmen Holding AS | Agriculture & fishing | 2022 |
| Silur AS | Real estate | 2004 |
| Silurveien 1-9 AS | Real estate | 2024 |
| Silurveien 20 AS | Real estate | 2023 |
| Silurveien 24N Og 24M AS | Real estate | 2024 |
| Silurveien 28 AS | Real estate | 2024 |
| Silurveien B24 AS | Real estate | 2022 |
| Silurveien B25 AS | Real estate | 2023 |
| Silverbay Britt Ross | Wholesale & retail | 2013 |
| Silverbay Consulting AS | Professional & scientific | 2011 |
| Silverlines AS | Wholesale & retail | 2008 |
| Simace Holding AS | | 2021 |
| Simon Creations AS | Wholesale & retail | 2024 |
| Simple Coaching AS | Education | 2025 |
| Simre AS | Financial services | 2011 |
| Sinar Holding AS | Financial services | 2011 |
| Sincerus AS | Real estate | 2011 |
| Sindland AS | Professional & scientific | 2013 |
| Sindland Jacobsen AS | Professional & scientific | 2018 |
| Singo Holding AS | | 2023 |
| Sinonordic AS | Administrative & support | 2006 |
| Sintech AS | Information & communication | 2019 |
| Sintu Holding AS | | 2021 |
| Sira Holding Sør AS | Health & social care | 2021 |
| Sirem AS | Real estate | 2005 |
| Siren Invest AS | | 2025 |
| Siri Urdal Holding AS | | 2022 |
| Sirius Asker AS | Real estate | 2012 |
| Sirius Enterprises AS | Information & communication | 2023 |
| Sirius Kristiansand AS | Real estate | 2012 |
| Sisaro AS | | 2025 |
| Siso Eiendom AS | Real estate | 2018 |
| Sissel Nordhagen Invest AS | Real estate | 2005 |
| Sisu Invest AS | Financial services | 2014 |
| Sitc AS | Professional & scientific | 2007 |
| Sitecom Kristiansand AS | Information & communication | 2022 |
| Sitek Ans | Professional & scientific | 1995 |
| Sitges AS | Financial services | 2013 |
| Sithpa AS | Other services | 2024 |
| Siv Arkitekt Janicke Jebsen Vinje AS | Professional & scientific | 2001 |
| Sivcon AS | Professional & scientific | 2006 |
| Sivilarkitekt Erik Asbjørnsen AS | Professional & scientific | 2012 |
| Siviling. J.B. Andersen AS | Professional & scientific | 2013 |
| Sivilingeniør Haakon Aasbø AS | Professional & scientific | 2011 |
| Siviløkonom Rune Øidne Reinertsen AS | Professional & scientific | 2022 |
| SJ Tools AS | Wholesale & retail | 2019 |
| SJ4 Treningssenter AS | Arts & recreation | 2024 |
| SJB Eiendomsinvest AS | Real estate | 2016 |
| SJB Invest AS | Real estate | 2004 |
| Sjeggestad Invest AS | | 2022 |
| Sjekk Regnskapet AS | Professional & scientific | 2021 |
| Sjekta AS | Construction | 2005 |
| Sji AS | Wholesale & retail | 2024 |
| SJT Miljø AS | Water & waste | 1998 |
| Sjø-Sport Eiendom AS | Real estate | 2020 |
| Sjø-Sport Holding AS | Wholesale & retail | 2019 |
| Sjø-Sport Kristiansand AS | Wholesale & retail | 1989 |
| Sjøberg Holding AS | | 2020 |
| Sjøfront Invest AS | | 2025 |
| Sjøhuset Eiendom AS | Real estate | 2015 |
| Sjøhuset Kontorer AS | Real estate | 2008 |
| Sjølystveien 9 AS | Real estate | 2024 |
| Sjølystveien Vakt AS | Hospitality | 2016 |
| Sjømannshjemmet AS | Real estate | 2015 |
| Sjøtransport AS | | 1978 |
| Skaar Holding & Invest AS | Professional & scientific | 2020 |
| Skaara Eiendom AS | Real estate | 2015 |
| Skabe AS | | 2021 |
| SKAG3RAK Arkitekter AS | Professional & scientific | 2025 |
| Skagen Pub AS | Hospitality | 2019 |
| Skagerak Capital AS | Financial services | 2014 |
| Skagerak Capital III AS | Financial services | 2016 |
| Skagerak Capital IV AS | Financial services | 2020 |
| Skagerak Capital V AS | Financial services | 2024 |
| Skagerak Dynamics AS | Professional & scientific | 2016 |