| SH Blikkenslagerverksted AS | Construction | 2017 |
| SH Regnskap AS | Professional & scientific | 2021 |
| Shala Capital AS | Real estate | 2019 |
| Shelf Side AS | | 2022 |
| Shiba Eiendom AS | Real estate | 2006 |
| Short Travel Education AS | Education | 2026 |
| Showy AS | | 2020 |
| Sidus Invest AS | | 2019 |
| Siesda Invest AS | Real estate | 2007 |
| Sigma Holding AS | Real estate | 2005 |
| Signal Sko AS | Wholesale & retail | 1992 |
| Signateur AS | Professional & scientific | 2016 |
| Sigvarts 3D Tegne Og Byggetjenester AS | Professional & scientific | 2022 |
| Siljanveien 55 AS | Professional & scientific | 2013 |
| Silkeblomsten Da | Arts & recreation | 1988 |
| Simo Marine AS | Professional & scientific | 2017 |
| Simonsen-Invest AS | Real estate | 2021 |
| Sinceris AS | | 2021 |
| Sinclair Capital Da | | 2025 |
| Sira Holding AS | | 2014 |
| Siri Krohn-Fagervoll AS | Professional & scientific | 2011 |
| Site Partners AS | Information & communication | 2023 |
| Siv Ing Anders D Johansen AS | Professional & scientific | 2014 |
| Sivert Blikk & Montasje AS | Construction | 2023 |
| Sivert Bolig AS | Real estate | 2022 |
| Sivert Holding AS | Construction | 2022 |
| Sivert Montasje AS | Construction | 2022 |
| Sivilarkitekt Silje Søntvedt AS | Professional & scientific | 2022 |
| Sivilingeniør Lars Tangerås AS | Professional & scientific | 2025 |
| SJ Holding AS | Financial services | 2005 |
| SJ Thaimat AS | Hospitality | 2025 |
| Sjekkpunkt Norge AS | Wholesale & retail | 1998 |
| SJN Holding AS | Real estate | 2022 |
| Sjø Consulting AS | Professional & scientific | 2012 |
| Sjøgren AS | Construction | 2020 |
| Sjørholt Invest AS | Construction | 2024 |
| SK Armering AS | Construction | 2017 |
| SK Property Invest AS | Real estate | 2019 |
| Skaadel Invest AS | Financial services | 2005 |
| Skaalen Holding AS | | 2026 |
| Skagerak Group AS | Administrative & support | 2015 |
| Skagerak Property AS | Real estate | 2025 |
| Skagerak Sikkerhet AS | Education | 2016 |
| Skagerakklinikken AS | Health & social care | 2021 |
| Skarheim Eiendom AS | Real estate | 2026 |
| Skarweld AS | Manufacturing | 1984 |
| Skategoods AS | Wholesale & retail | 2020 |
| Skau Holding AS | Real estate | 2006 |
| Skau Invest AS | Real estate | 2011 |
| Skauen Kristelige Barnehage AS | Education | 2020 |
| Skeidar Skien AS | Wholesale & retail | 1997 |
| Skerve Holding AS | | 2019 |
| Skien Auto AS | Wholesale & retail | 2018 |
| Skien Autosenter AS | Wholesale & retail | 2016 |
| Skien Autosenter Service AS | Administrative & support | 2024 |
| Skien Batteri & Energiservice AS | Wholesale & retail | 2019 |
| Skien Begravelsesbyrå AS | Other services | 1988 |
| Skien Bilformidling AS | Wholesale & retail | 2022 |
| Skien Bilforum AS | Wholesale & retail | 2020 |
| Skien Bilsalg AS | Wholesale & retail | 2018 |
| Skien Bilskade & Verksted AS | Other services | 2010 |
| Skien Bilskade Og Verksted Holding AS | Health & social care | 2016 |
| Skien Blikkenslagerverksted AS | Construction | 1997 |
| Skien Bolig AS | Real estate | 2025 |
| Skien Byggservice AS | Construction | 2020 |
| Skien Confekthjørnet AS | Hospitality | 2023 |
| Skien Containerservice AS | Water & waste | 2006 |
| Skien Dalen Skipsselskap AS | Transport & logistics | 1992 |
| Skien Eiendomsutvikling AS | Real estate | 2018 |
| Skien Elektro AS | Construction | 2014 |
| Skien Fysikalske Institutt Og Akupunktur Da | Health & social care | 1970 |
| Skien Gokart Utleie AS | Administrative & support | 2012 |
| Skien Hifi AS | Wholesale & retail | 2025 |
| Skien Hudlegesenter AS | Health & social care | 2021 |
| Skien Hudpleie AS | Other services | 2001 |
| Skien Invest AS | Real estate | 2019 |
| Skien Isbar Da | Hospitality | 2010 |
| Skien Kjøkken Og Møbellakkering AS | Manufacturing | 2021 |
| Skien Kjøttforretning AS | Wholesale & retail | 2021 |
| Skien Live AS | Arts & recreation | 2013 |
| Skien Maskin AS | Construction | 2017 |
| Skien Møbler AS | Wholesale & retail | 2005 |
| Skien Optikk AS | Wholesale & retail | 2006 |
| Skien Parfymeri AS | Wholesale & retail | 2019 |
| Skien Parkering AS | Real estate | 2019 |
| Skien Regnskapskontor AS | Professional & scientific | 1987 |
| Skien Ridesenter AS | Education | 2022 |
| Skien Rør Og Flis AS | Construction | 2006 |
| Skien Rørservice AS | Construction | 2021 |
| Skien Sportsbar AS | Hospitality | 2018 |
| Skien Struts Da | Agriculture & fishing | 1998 |
| Skien Tak Og Fasade AS | Construction | 2026 |
| Skien Takst AS | Real estate | 2024 |
| Skien Tannhelse AS | Health & social care | 2025 |
| Skien Tannhelse Da | Health & social care | 2009 |
| Skien Tannlegesenter Skien Tannlegevakt AS | Health & social care | 2020 |
| Skien Tannregulering AS | Health & social care | 2020 |
| Skien Taxi Buss AS | Transport & logistics | 2011 |
| Skien Taxi SA | Transport & logistics | 1917 |
| Skien Tomteselskap AS | Construction | 1964 |