| RT Shore Power AS | Energy | 2020 |
| Rtka AS | Wholesale & retail | 2022 |
| RTR Holding AS | | 2024 |
| Rune Aasbø Lystad AS | Health & social care | 2017 |
| Rustadveien 15/17 Limited Nuf | Real estate | 2026 |
| Røseth Bygg Og Betong AS | Construction | 2020 |
| Saguaro Holding AS | Health & social care | 2021 |
| Saldo Regnskap AS | Professional & scientific | 1994 |
| Sander Akselsen Holding AS | Construction | 2022 |
| Sangterapi AS | Arts & recreation | 2024 |
| Sanness Eiendom AS | Manufacturing | 2006 |
| Sardinfabrikken AS | Hospitality | 2024 |
| Security First AS | Wholesale & retail | 2017 |
| Sell Holding AS | Real estate | 2021 |
| Semta Eiendom AS | Real estate | 2024 |
| Semta Holding AS | Wholesale & retail | 2014 |
| Sfis AS | | 2025 |
| Sigarcom AS | Wholesale & retail | 2001 |
| Sigbjørn Bråtane Holding AS | Professional & scientific | 2005 |
| Sigbjørn Tønnesland AS | Real estate | 2005 |
| Sigtor AS | Real estate | 2000 |
| Sissil AS | Hospitality | 2005 |
| Sjøsenteret Risør AS | Manufacturing | 1986 |
| Skalldyr Risør AS | Agriculture & fishing | 2025 |
| Skibvika Bryggesamvirke SA | Arts & recreation | 2017 |
| Skiveien Snørydding AS | Administrative & support | 2024 |
| Skjeldsø Marina Og Utleie AS | Real estate | 2013 |
| Skjærhue AS | Wholesale & retail | 2006 |
| Skrue Mcduck AS | | 2025 |
| Skyville Networks Ltd Nuf | Professional & scientific | 2019 |
| Smedby Bygg Og Anlegg AS | Construction | 2005 |
| Smedby Eiendom AS | Real estate | 2005 |
| Små-Sten AS | Real estate | 1981 |
| So Risør AS | Hospitality | 2026 |
| Sofie Holding AS | Real estate | 2020 |
| Sofienberg AS | Real estate | 2020 |
| Sollie Bygg AS | Construction | 2003 |
| Sollie Bygg Dagfinn Sollie Og Arvid Sollie Ans | Construction | 1998 |
| Sollie Bygg Eiendom-Dagfinn Sollie Og Arvid Sollie Ans | Real estate | 2001 |
| Sollie Holding AS | Construction | 2005 |
| Sollie Og Fidje Bygg AS | Construction | 2000 |
| Solsiden 1 AS | Real estate | 1937 |
| Solsiden 40 AS | Professional & scientific | 2014 |
| Solsiden 40 Invest AS | Professional & scientific | 2022 |
| Solsiden 8 AS | | 2003 |
| Solstad-Holding AS | Financial services | 2005 |
| Songe Holding AS | | 2026 |
| Sourceit AS | Information & communication | 2012 |
| Spina AS | Health & social care | 1989 |
| Sport 1 Risør AS | Wholesale & retail | 1999 |
| Stake Invest AS | | 2022 |
| Stavelin AS | Wholesale & retail | 2007 |
| Storegjerde Eiendom AS | Real estate | 2021 |
| Stranden 1 AS | Real estate | 2002 |
| Stranden Risør AS | Hospitality | 2021 |
| Strandgaten 23 AS | Real estate | 2013 |
| Studio M Risør AS | Other services | 2023 |
| Sunde Investment AS | | 2023 |
| Supercap Technologies AS | Professional & scientific | 2024 |
| Svada Retail AS | Wholesale & retail | 2025 |
| Sveha Eiendom AS | Real estate | 2000 |
| SWH Invest AS | Real estate | 2005 |
| Sørfjord AS | Administrative & support | 2010 |
| Sørfjorden Vann Og Avløp AS | Water & waste | 2013 |
| Sørlandet Feriesenter AS | Hospitality | 2005 |
| Sørlandet Hytter Og Hus AS | | 2007 |
| Sørlandske Transport AS | Transport & logistics | 1994 |
| Sørtakst AS | Real estate | 2010 |
| T-K Eiendom AS | Construction | 2024 |
| Tak Og Bolig AS | Construction | 2026 |
| Takstingeniør Mesel AS | Construction | 2008 |
| Tangengt. 12 AS | Real estate | 2005 |
| Tann Eiendom AS | Real estate | 2001 |
| Tann for Tann AS | Health & social care | 2021 |
| Tannlege Anne Aamlid AS | Health & social care | 2023 |
| Tannlege Ellen Christine Vigen AS | Health & social care | 2003 |
| Tannlege Ellen Christine Vigen Holding AS | Health & social care | 2013 |
| Tannlege Erik Nilsen AS | Health & social care | 2005 |
| Tannlege Sverre Aukland AS | Health & social care | 2003 |
| Taraldlien Bygg AS | Construction | 2024 |
| TB Risør AS | Real estate | 2026 |
| Tech Media Østergren Og Gustavsen Da | Administrative & support | 1986 |
| Tell Con Holding AS | Information & communication | 2024 |
| Tell Con Play AS | Information & communication | 2024 |
| Tempe AS | Information & communication | 2018 |
| Tetre AS | Real estate | 2005 |
| Tharaldsen Teknikk AS | Professional & scientific | 2023 |
| Thh-Holding AS | | 2026 |
| Tig Partners AS | Real estate | 2013 |
| Tjenna Barnehage AS | Education | 2015 |
| Tka Eiendom AS | Real estate | 1989 |
| Tollboden Risør AS | Real estate | 2021 |
| Tolpinrud Torg AS | Real estate | 2017 |
| Toma Bygg Og Eiendom AS | Real estate | 2014 |
| Torgersen S. Invest AS | | 2022 |
| Torjusen Brannservice AS | Professional & scientific | 2014 |
| Torskeberg Vannverk SA | Water & waste | 1968 |
| Tre for En AS | Health & social care | 2019 |
| Trevaren Eiendom AS | Real estate | 2004 |
| TRK Holding AS | | 2017 |