| Studioxo AS | Arts & recreation | 2021 |
| Stulen Trading AS | Wholesale & retail | 1996 |
| Sturgeon Holding AS | Energy | 2020 |
| STW Holding AS | | 2026 |
| Stølekilen AS | Real estate | 2020 |
| Støylane-Vegen | Real estate | 1995 |
| Sukasen Studio Ans | Information & communication | 2024 |
| Sukka Holding AS | Construction | 2008 |
| Sultana Gallery AS | Wholesale & retail | 2025 |
| Sunniva Grava AS | Wholesale & retail | 2020 |
| Super App AS | Information & communication | 2026 |
| Superbarna AS | Wholesale & retail | 2017 |
| Superknut Invest AS | Real estate | 2016 |
| Supertune AS | Wholesale & retail | 2015 |
| SV Anlegg AS | Construction | 2023 |
| Svale Invest AS | Real estate | 2005 |
| Svamax AS | Real estate | 2021 |
| Svanberg Byggteknikk AS | Professional & scientific | 2019 |
| Svanen Apotek AS | Wholesale & retail | 2023 |
| Svanstul Utvikling AS | Real estate | 2006 |
| Svendsen Eksos Holding AS | Other services | 2013 |
| Svendsen Eksos Skien AS | Other services | 1998 |
| Sverresgate 20 AS | Real estate | 2007 |
| Svevr AS | Professional & scientific | 2023 |
| Svevr Trøndelag AS | Administrative & support | 2026 |
| Svindal Consulting AS | Professional & scientific | 2019 |
| Svindal Holding AS | Professional & scientific | 2012 |
| Svineroi AS | Real estate | 1991 |
| Sweet Holding AS | Arts & recreation | 2005 |
| Sweetheart Ans | Wholesale & retail | 1990 |
| Swift AS | | 2021 |
| Swiftner AS | Information & communication | 2023 |
| Sybutikken Skien Ans | Wholesale & retail | 1997 |
| Sydhavsreiser Let's Travel AS | Administrative & support | 2007 |
| Sykkel Bjørn AS | Wholesale & retail | 2016 |
| Sykkelbryggeriet AS | Hospitality | 2024 |
| Synoru AS | Information & communication | 2020 |
| System Kjøkken AS | Manufacturing | 2022 |
| Såperiet AS | Wholesale & retail | 2021 |
| Søndre Bjørntvedt Utvikling AS | Real estate | 2021 |
| Søndre Hyni Gård AS | Real estate | 2016 |
| Søndre Sandøya Va Lag SA | Water & waste | 2014 |
| Sønstebø Utvikling AS | Real estate | 2006 |
| Sør & Sør AS | Construction | 1972 |
| Sør-Øst Spesialistsenter AS | Health & social care | 1994 |
| Sørbø Eiendom AS | Real estate | 2001 |
| Søreid AS | Transport & logistics | 2017 |
| Sørensen AS | Administrative & support | 1992 |
| Sørensen Maskin AS | Construction | 1980 |
| Sørensengården AS | Professional & scientific | 1979 |
| Søretjenn Utvikling AS | Real estate | 2021 |
| Sørstua AS | Manufacturing | 2018 |
| Sørøst Brannsikkerhet AS | Professional & scientific | 2022 |
| Søtvedt Holding AS | Transport & logistics | 2017 |
| Søtvedt Maskin AS | Transport & logistics | 2017 |
| Søvik & Hegna AS | Real estate | 2002 |
| T a Betong Og Montasje AS | Construction | 2025 |
| T Claussen Holding AS | Real estate | 2022 |
| T Midgaard & Co AS | Manufacturing | 1998 |
| T Olsen Holding AS | | 2021 |
| T R Holding AS | Wholesale & retail | 2016 |
| T R Invest AS | Wholesale & retail | 2016 |
| T&S Audio AS | | 2020 |
| T-Gruppen AS | Energy | 2022 |
| T. Amundsen Holding AS | Wholesale & retail | 2020 |
| T. Engh Holding AS | Construction | 2020 |
| T. Kjellsen Holding AS | Real estate | 2005 |
| T.A. Holding AS | Real estate | 2008 |
| T.B Holding AS | Financial services | 2008 |
| T.E.K. Holding AS | Financial services | 2014 |
| T.Gustavsen AS | Professional & scientific | 2024 |
| T.L. Eiendom AS | Wholesale & retail | 2006 |
| Ta Invest AS | Construction | 2023 |
| Taalund Holding AS | Financial services | 2005 |
| Tablers Investments AS | Health & social care | 2021 |
| Tah AS | | 2014 |
| Taher Flis Og Maling AS | Construction | 2025 |
| Tak-Leverandøren AS | Wholesale & retail | 1990 |
| Takaro AS | Real estate | 2016 |
| Takfornying Telemark AS | Construction | 2016 |
| Takfornying Telemark Holding AS | Construction | 2025 |
| Taklift AS | Transport & logistics | 1993 |
| Takmontasje AS | Construction | 2024 |
| Taksera AS | Real estate | 2026 |
| Takstforum Telemark AS | Professional & scientific | 2016 |
| Taksttjenester Grenland AS | Real estate | 2015 |
| Takvurdering AS | Professional & scientific | 2026 |
| Tandberg Revisjon AS | Professional & scientific | 2024 |
| Tangedal Johansen Holding AS | | 2018 |
| Tangen Utvikling AS | Real estate | 2010 |
| Tangens Eiendom AS | Real estate | 2018 |
| Tanktrail AS | Transport & logistics | 2013 |
| Tannlege Ane Marte Sletten Stamnes AS | Health & social care | 2021 |
| Tannlege Kari Nesse AS | Health & social care | 2010 |
| Tannlege Kenneth Bergan AS | Health & social care | 2023 |
| Tannlege Laila AS | Health & social care | 2017 |
| Tannlege Margrethe Kjellsen Westlie AS | Health & social care | 2024 |
| Tannlege Nooshin Eslampour AS | Health & social care | 2026 |
| Tannlege Per Hauge AS | Health & social care | 2025 |
| Tannlege Sondre Lunde Skjødtsvoll AS | Health & social care | 2025 |