| Spind Treindustri AS | Manufacturing | 1982 |
| Spinnvill Auto AS | Wholesale & retail | 2019 |
| Spinnvill Eiendom AS | Real estate | 2019 |
| Sport 1 Mandal AS | Wholesale & retail | 2020 |
| SS Barden AS | Real estate | 2002 |
| SSH091011 AS | Real estate | 2017 |
| ST. Elvegt 106 AS | Real estate | 2005 |
| ST. Helena Invest AS | Wholesale & retail | 2005 |
| Stakkhauen AS | Real estate | 1994 |
| Staman Eiendom AS | Real estate | 2003 |
| Stangeland & Co Advokatfirma AS | Professional & scientific | 2012 |
| Stangeland AS | Real estate | 2018 |
| Star Island Holding AS | Wholesale & retail | 2005 |
| Start Trafikkskole AS | Education | 2020 |
| Stisdalsveien 7 AS | Real estate | 2023 |
| Stisdalsveien Næringsutleie AS | Real estate | 2025 |
| Stonkus Invest AS | | 2019 |
| Store Elvegate 25 AS | Real estate | 2013 |
| Store Elvegate 40 AS | Real estate | 2013 |
| Store Elvegate 42-43 AS | Real estate | 2004 |
| Store Elvegt 22 AS | Real estate | 2005 |
| Storm Network AS | Information & communication | 2021 |
| Storvig AS | Agriculture & fishing | 2020 |
| Strataquip AS | Professional & scientific | 2021 |
| Straviso AS | Professional & scientific | 2025 |
| Strekkmetall AS | Wholesale & retail | 2013 |
| Strong Equity AS | Real estate | 2020 |
| Strømdaljordet 58 AS | Real estate | 2020 |
| Studio 254 AS | Professional & scientific | 2026 |
| Studio E Stensby AS | Education | 2012 |
| Studio Liz AS | Other services | 2026 |
| Stusvik Holding AS | | 2005 |
| Stusvikheia Næringspark AS | Real estate | 2017 |
| STV Invest AS | | 2024 |
| Støle Glasservice AS | Construction | 2017 |
| Støle Næringsbygg AS | Real estate | 2011 |
| Submatech AS | Professional & scientific | 2013 |
| Suleskard Masseuttak AS | Mining & quarrying | 2007 |
| Sumalees Kjøkken AS | Hospitality | 2021 |
| Suncel AS | Wholesale & retail | 2022 |
| Sundial AS | Wholesale & retail | 2014 |
| Sunsense AS | Professional & scientific | 2014 |
| Suntin Ans | Construction | 2011 |
| Susk AS | Hospitality | 2023 |
| Svein Høksaas AS | Professional & scientific | 2006 |
| Svenn Iglebæk AS | Wholesale & retail | 2006 |
| Svensson Invest AS | | 2025 |
| Svåbekk 15 AS | Real estate | 2018 |
| SW Sports AS | Professional & scientific | 2023 |
| Syd Utemiljø AS | Administrative & support | 2021 |
| Sydlixt AS | Real estate | 2025 |
| System Bygg AS | Construction | 1994 |
| Syvert Invest AS | Real estate | 2021 |
| Syvhav AS | | 2024 |
| Schmidt AS | Real estate | 1985 |
| Sølvis Hud & Makeup Studio AS | Other services | 2022 |
| Sølvskonnerten AS | Information & communication | 2025 |
| Sør Entreprenøran AS | Real estate | 2022 |
| Sør Import Eiendom AS | Real estate | 2012 |
| Sør Lydutleie Ans | Administrative & support | 2024 |
| Sør Opplag Eiendom AS | Real estate | 2026 |
| Sørbåt AS | Wholesale & retail | 2020 |
| Sørensen Tekniske AS | Administrative & support | 2020 |
| Sørlandets Elektro AS | Construction | 2011 |
| Sørlandets Elektro Eiendom AS | Real estate | 2015 |
| Sørlandseiendom AS | Real estate | 2017 |
| Sørlandshus AS | Construction | 2017 |
| Sørlandsreklame AS | Manufacturing | 2005 |
| Søyland-Øen Da | Manufacturing | 2019 |
| T Bang G AS | Professional & scientific | 1998 |
| T Invest AS | Real estate | 2004 |
| T O Jensen AS | Real estate | 2005 |
| T.E.S Holding AS | | 2021 |
| T.I.B Holding AS | | 2020 |
| T.S.B Invest AS | Real estate | 2014 |
| T/O Service AS | Wholesale & retail | 2025 |
| Take AS | | 2025 |
| Tann Sør AS | Health & social care | 2022 |
| Tannlege Irene Kleven AS | Health & social care | 2009 |
| Tannlege Lien Nguyen AS | Health & social care | 2004 |
| Tannlege Line CH. Holtan AS | Health & social care | 2016 |
| Tannlegene Franke Og Ungerechts AS | Health & social care | 2022 |
| Tannlegene På Brygga AS | Health & social care | 2002 |
| Tas AS | Real estate | 2007 |
| TBR Holding 1 AS | Real estate | 2018 |
| TD Tånevik Anlegg AS | Administrative & support | 2024 |
| Team Maudal AS | Health & social care | 2023 |
| Team Skaar Holding AS | | 2026 |
| Team Trafikkskole Mandal AS | Education | 2016 |
| Teamweld AS | Professional & scientific | 2017 |
| Techno Eiendom AS | Real estate | 1995 |
| Techno Innova Kompetanse AS | Information & communication | 2025 |
| Tegas AS | Real estate | 2019 |
| Teina-Pedersen AS | Agriculture & fishing | 2023 |
| Teinsvollen AS | Real estate | 2020 |
| Tellaus Holding AS | Real estate | 2005 |
| Tenk HR AS | Professional & scientific | 2024 |
| Tennis 360 AS | Education | 2015 |
| Ter-Consult AS | Professional & scientific | 2015 |
| Termovisjon Sør AS | Professional & scientific | 2005 |