| Rørestrand Camping Drift AS | Hospitality | 2020 |
| Rørestrand Eiendom AS | Real estate | 1937 |
| Rørestrandsveien Utvikling AS | Real estate | 2016 |
| S-T-E Holding AS | Financial services | 2005 |
| Salvus AS | Professional & scientific | 1997 |
| Samsteg Veiledningstjeneste AS | Education | 2024 |
| Samvirkeforetaket Odd Fellow- Og Rebekkalogene I Horten | Real estate | 1999 |
| Sande Næringspark AS | Construction | 2008 |
| Sandquist Elektro AS | Construction | 2016 |
| Sandviks Båtbyggeri AS | Manufacturing | 2006 |
| Sapience AS | Professional & scientific | 2024 |
| Saxon King Holding AS | Hospitality | 2024 |
| SC Solutions AS | Construction | 2024 |
| Scanoffice OY | Wholesale & retail | 2009 |
| Schaathun AS | Education | 2024 |
| Schaathun Undervisning AS | Education | 2024 |
| Se-Mont AS | Manufacturing | 2007 |
| Sebastian Zalo AS | Arts & recreation | 2022 |
| Selvig & Co AS | Manufacturing | 2005 |
| Selvig AS | Manufacturing | 2011 |
| Semb Hovedgård AS | Real estate | 2020 |
| Semenov Invest AS | | 2022 |
| Sentrum Legekontor Horten AS | Health & social care | 2023 |
| Servcon AS | Construction | 2019 |
| Servicepro AS | Transport & logistics | 2024 |
| Shiyar Frisør AS | Other services | 2022 |
| Sial Food Ans | Hospitality | 2008 |
| Sibako AS | Financial services | 2006 |
| Siddiqi AS | Wholesale & retail | 2020 |
| Sigvartsen Bygg Og Anlegg AS | Construction | 2016 |
| Sihmore AS | Administrative & support | 2023 |
| Silje Bornø Andersen AS | Wholesale & retail | 2016 |
| Silje Hvarnes AS | | 2024 |
| Silvasti AS | Transport & logistics | 2016 |
| Sim-Mech AS | Professional & scientific | 2023 |
| Simply Nordic AS | Wholesale & retail | 2020 |
| Simrad AS | Manufacturing | 2007 |
| Singh Tech AS | Real estate | 2019 |
| Sir Holding AS | Professional & scientific | 2005 |
| Sislebekk Skog Ans | Agriculture & fishing | 2024 |
| Sislebekk Skog AS | Real estate | 2006 |
| Siste Tee AS | Hospitality | 2024 |
| Sivi AS | Hospitality | 2015 |
| Sivilingeniør Jon-Arild Andreassen AS | Professional & scientific | 2014 |
| Sivstranda AS | Real estate | 2024 |
| Sjøblom AS | Manufacturing | 2007 |
| Skaarud Forvaltning AS | Real estate | 1997 |
| Skagerak Panorama AS | Real estate | 2023 |
| Skarsnuten Eiendom AS | Real estate | 1999 |
| Skarsnuten Hotell AS | Real estate | 2003 |
| Skilnand AS | | 2024 |
| Skoleelektronikk Ing Hogstad Ans | | 1990 |
| Skrim Hytteutleie AS | Real estate | 2020 |
| Skrukketrollet Familiebarnehage Da | Education | 2004 |
| Slettemark Holding AS | | 2022 |
| Sletterød Holding AS | Real estate | 2005 |
| Smak Av Horten AS | | 2017 |
| Smeb AS | Arts & recreation | 2022 |
| SMS Hotell Drift AS | Hospitality | 2004 |
| SMÅDYRKLINIKK1 AS | Professional & scientific | 2024 |
| Snacks AS | Wholesale & retail | 2018 |
| Solerødveien AS | Real estate | 2015 |
| Solhøy Frukt Og Tobakk AS | Wholesale & retail | 2017 |
| Solhøy Lounge AS | Hospitality | 2024 |
| Solhøyden AS | Real estate | 2025 |
| Sollistrand Eiendom AS | Real estate | 1982 |
| Solvik Konsulenttjenester AS | Professional & scientific | 2023 |
| Som Avtalt AS | Professional & scientific | 2008 |
| Sonoco-Alcore AS | Wholesale & retail | 1984 |
| Soulsville Holding AS | | 2019 |
| South-East Invest AS | | 2026 |
| Speed Trafikkopplæring AS | Education | 2008 |
| Speleoconsult AS | Professional & scientific | 2019 |
| Sponk Ans | Information & communication | 2000 |
| Sport Import Horten Ans | Wholesale & retail | 1996 |
| Sport Scandinavia AS | Wholesale & retail | 2020 |
| SPORT1 Horten AS | Wholesale & retail | 2006 |
| Sprinx Nordic AS | Manufacturing | 2021 |
| Stangsgate 5 Åsgårdstrand AS | Real estate | 2022 |
| Stasjonsdrift Torstensrud AS | Wholesale & retail | 2019 |
| Steambit AS | Information & communication | 2021 |
| Stein Lie AS | Financial services | 2005 |
| Stein Og Fasade AS | Construction | 2020 |
| Steiner Bygg AS | Wholesale & retail | 2016 |
| Steiner VVS AS | Construction | 2023 |
| Stenly AS | Financial services | 2005 |
| Stensaa AS | Professional & scientific | 2014 |
| Stensnes Invest AS | | 2025 |
| Stephans Murer Service AS | Construction | 2016 |
| Stetzer AS | Wholesale & retail | 2021 |
| Stgt Tretre AS | Real estate | 2026 |
| Stones Holding AS | | 2026 |
| Storgata 117 AS | Real estate | 2013 |
| Storgata 21 Horten AS | Real estate | 2021 |
| Storgata 34 AS | Real estate | 2017 |
| Storgata 40 Ans | Real estate | 2003 |
| Storgata 72 Holding AS | Real estate | 2018 |
| Storgata 9-11 AS | Real estate | 2006 |
| Storgata Eiendom AS | Real estate | 1993 |
| STORGATA-20 AS | Real estate | 2018 |