| Sletner Holding AS | | 2005 |
| Slettevold Bussreiser AS | Transport & logistics | 2012 |
| Slippen Holding AS | Hospitality | 2014 |
| Slipsteinneset 19 AS | Manufacturing | 2010 |
| Smakslykke Fredrikstad AS | Wholesale & retail | 2024 |
| Smalgangen Eiendom AS | Real estate | 2017 |
| Smashdessert AS | Hospitality | 2026 |
| Smedskaret Eiendom AS | Real estate | 2022 |
| SMH Eiendom AS | Real estate | 2018 |
| Smykkeverksted AS | Manufacturing | 2018 |
| Snute AS | Information & communication | 2024 |
| Snæbbus Hair Helsehuset AS | Other services | 2013 |
| Snæbbus Hair Holding AS | Other services | 2013 |
| Sofia Knudsen AS | Arts & recreation | 2026 |
| Sol Boligkonsulent AS | Professional & scientific | 2014 |
| Solbergs Terapi Og Kommunikasjons Tjenester AS | Health & social care | 2026 |
| Solibo Fredrikstad AS | Real estate | 2002 |
| Solsiden Eiendom AS | Real estate | 2003 |
| Solskjerming AS | Wholesale & retail | 2013 |
| Solveigs Pizza Fredrikstad AS | Hospitality | 2012 |
| Sosiodata Ans | Administrative & support | 1990 |
| Spanor Holding AS | Real estate | 2022 |
| Spesialistklinikken Kråkerøy AS | Health & social care | 2025 |
| Spider Media AS | Professional & scientific | 2003 |
| Sredna AS | Real estate | 2019 |
| ST Croix Capital AS | | 2000 |
| ST. Marie Gate 95 AS | Real estate | 2022 |
| Stadionklinikken AS | Health & social care | 2011 |
| Steg Holding Fredrikstad AS | Real estate | 2016 |
| Steinar Sælid AS | Manufacturing | 1993 |
| Stepp Holding AS | | 2020 |
| Sterk Kommunikasjon AS | Professional & scientific | 2002 |
| Stjernstedt Eiendom AS | Real estate | 2006 |
| Storgata 71 AS | Real estate | 1995 |
| Storgaten 18 Son AS | Real estate | 1985 |
| Strandli Transport AS | Transport & logistics | 2012 |
| Straye Gruppen AS | Construction | 2019 |
| Straye Hybridbygg AS | Construction | 2023 |
| Straye Industri AS | Construction | 2023 |
| Straye Montasje AS | Construction | 2021 |
| Straye Stålbygg AS | Construction | 2007 |
| Straye Tak AS | Construction | 2022 |
| Straye Trebygg AS | Construction | 2019 |
| Structor Prosjekt AS | Professional & scientific | 2018 |
| Structor Teknisk Rådgivning AS | Professional & scientific | 2016 |
| Studio by KK Værste AS | Wholesale & retail | 2025 |
| Studio Hov AS | Professional & scientific | 2023 |
| Studio Wallin AS | Professional & scientific | 2024 |
| Studium Actoris Ans | Arts & recreation | 1999 |
| Styrefart AS | Education | 2024 |
| Stålbygg AS | Manufacturing | 2014 |
| Stø-Ansatte Ans | Financial services | 2007 |
| Stødig AS | Professional & scientific | 2015 |
| Sundholm Eiendom AS | Real estate | 2011 |
| Sunfast AS | Wholesale & retail | 2022 |
| Svanesund AS | Agriculture & fishing | 2024 |
| Svensen Holding AS | Real estate | 2007 |
| SVT Invest AS | Real estate | 2017 |
| Swensen Invest Og Eiendom AS | Real estate | 2016 |
| Synnes Blomster AS | Wholesale & retail | 2026 |
| Stop Elektro AS | Construction | 1987 |
| Sæter Bringager Ans | Wholesale & retail | 2001 |
| Søfuco AS | | 2025 |
| Sørbøe Holding AS | Real estate | 2007 |
| Sørlie AS | Agriculture & fishing | 2020 |
| Sørlie Næringseiendom AS | Real estate | 2018 |
| Sørlie Og Sørlie AS | Professional & scientific | 2005 |
| Ta Eiendom Og Hytteservice AS | Real estate | 2024 |
| Talsnes Invest AS | | 2025 |
| Tannlege Haabeth AS | Health & social care | 2014 |
| Taranaki AS | Information & communication | 2003 |
| Tasting Game Holding AS | Wholesale & retail | 2016 |
| TBM AS | Transport & logistics | 2006 |
| Teatergruppa Forum Ans | Arts & recreation | 1997 |
| Tech Hub AS | Information & communication | 2017 |
| Teddy Eiendom AS | Real estate | 2001 |
| Televolden AS | Financial services | 2006 |
| Tellusalie Da | Arts & recreation | 2009 |
| Thermolux AS | Manufacturing | 2000 |
| Thoma Production AS | Professional & scientific | 1992 |
| Thorleif Sire AS | Professional & scientific | 2005 |
| Thorsen Capital AS | | 2026 |
| Tinda AS | Financial services | 2016 |
| Tivoli AS | Professional & scientific | 2019 |
| Tjenestecompagniet AS | Administrative & support | 2007 |
| TK Simensen Holding AS | | 2026 |
| TNB Værste AS | Wholesale & retail | 2024 |
| Ton-Tec AS | Construction | 2020 |
| Tore Eriksen Holding AS | Real estate | 2023 |
| Total Byggentreprenør AS | Construction | 2024 |
| Totex AS | Wholesale & retail | 2019 |
| Towerland AS | Professional & scientific | 2019 |
| Tpa-Holding AS | | 2020 |
| Trdl AS | Wholesale & retail | 2021 |
| Trikkærn Byggtjenester AS | Construction | 2013 |
| Trio Barneklær AS | Wholesale & retail | 2005 |
| Triple Loop AS | | 2018 |
| Trolldalen Bistand AS | Health & social care | 2016 |
| Trumpet Jungle Records AS | Arts & recreation | 2023 |
| Tunetek AS | Information & communication | 2020 |