| Raseborgs Fysioterapi Ab | Health & social care | 2001 |
| Raseborgs Företagstjänst Ab | Professional & scientific | 2010 |
| Raseborgs Hyresapotek Ab Oy | Real estate | 2022 |
| Raseborgs Kylservice Oy Ab | Construction | 2020 |
| Raseborgs Skärsgårdsservice - Raaseporin Saaristopalvelu OyAb | Construction | 2008 |
| Raseborgsmässan Ab Raaseporinmessut Oy | Administrative & support | 2014 |
| Rasetek Oy Ab | Construction | 2026 |
| Rasmet Steel Oy Ab | Wholesale & retail | 2013 |
| Rastas & Löfberg Avoin yhtiö Öppet bolag | Agriculture & fishing | 2016 |
| Ratios Oy Ab | Administrative & support | 2012 |
| Rehn F & P Kb | Water & waste | 1989 |
| Renesans Consulting Oy | Professional & scientific | 2014 |
| Rent Driving Oy | Administrative & support | 1990 |
| Robban Group Oy | Other services | 1993 |
| Rogus Oy | Real estate | 1984 |
| Rombergs Metall och Maskin öppet bolag | Manufacturing | 2018 |
| Rubuscum Oy Ab | Real estate | 1987 |
| Rääkkylän Kauppa O/Y | Real estate | 1930 |
| SA-LA Marine Ab Oy | Manufacturing | 2004 |
| SBA Industries Ab | Professional & scientific | 2025 |
| SBA Interior Oy | Manufacturing | 1987 |
| SBS Auto OY | Wholesale & retail | 2019 |
| SC INFRA Oy | Construction | 2024 |
| SE Capital Ab | Real estate | 2010 |
| SF Padel Ab Oy | Arts & recreation | 2021 |
| SJÖBBES Logistics Ab | Transport & logistics | 2024 |
| SL-Shipping & Logistics Oy Ab | Transport & logistics | 2005 |
| STEAX Ab | Professional & scientific | 2021 |
| Saldo & Saha Oy Ab | Professional & scientific | 2025 |
| Sandnäs Kauppa ja Kahvila Osuuskunta, Sandnäs Butik och Cafe Andelslaget | Wholesale & retail | 2014 |
| Sandnäsudd Hamn Ab | Hospitality | 2021 |
| Santun Seitan oy | Wholesale & retail | 2018 |
| Sarepa Oy | Construction | 2006 |
| Satumainen Tapahtumamarkkinointi Oy | Professional & scientific | 1996 |
| Scanopt Oy | Arts & recreation | 2019 |
| Seandrea Oy Ab | Other services | 2019 |
| Seaside Lifestyle Oy | Wholesale & retail | 2013 |
| See-Invest Ab | Financial services | 1987 |
| Selenius Construction & Consulting Oy | Construction | 2021 |
| Sense-Invest Ab | Financial services | 1985 |
| SeuRic Oy | Financial services | 2017 |
| Seulatek Oy | Manufacturing | 1988 |
| Signwell Oy | Manufacturing | 1997 |
| Sihi Cymbals Oy | Wholesale & retail | 2021 |
| Silentia Oy | Wholesale & retail | 2019 |
| Silfver Hunting & Catering Oy | Other services | 2022 |
| Silmälaboratorio Tono Oy | Health & social care | 1985 |
| Silvatjänst Ab | Agriculture & fishing | 1993 |
| Simgo Oy Ab | Information & communication | 2016 |
| Simke Oy | Real estate | 2004 |
| Sjagga Oy | Financial services | 1992 |
| Skatter Oy | Financial services | 2022 |
| Skogstjänst Karlsson Ab | Agriculture & fishing | 2015 |
| SkyRose Investment Ab | Real estate | 2024 |
| Skärgårdens vattenandelslag | Water & waste | 2022 |
| Skärgårds Bygg och Transport Ab | Construction | 2021 |
| Snack's Center Kb | Hospitality | 1982 |
| Snappertuna HGH-Bygg Ab | Construction | 1990 |
| Solvetek Oy | Administrative & support | 1995 |
| Solvik-Center Oy | Real estate | 1994 |
| Sommarö Basic Stone Oy | Manufacturing | 1995 |
| Sommaröstrand Kb | Manufacturing | 1983 |
| South Terra Acera Ab Oy | Professional & scientific | 2026 |
| Sparkmasters Oy | Manufacturing | 2022 |
| Sport- och elaffär B. Borg & Co | Wholesale & retail | 1966 |
| StagePoint Enterprises Ab | Arts & recreation | 2025 |
| Stageco Scandinavia Oy Ab | Administrative & support | 1992 |
| Stageco Trucks Ab | Transport & logistics | 2005 |
| Stallet Ekenäs AB | Hospitality | 2021 |
| Stallörens Betjäningscentrum Kb | Wholesale & retail | 1985 |
| Stella Nord Invest Ab | Professional & scientific | 2016 |
| Stig Saarinen Ky | Education | 2010 |
| Strömsö Property Development Oy | Real estate | 2004 |
| Strömsö Resort & Club Oy | Arts & recreation | 2021 |
| Strömsön Huvilarakennus Oy | Construction | 2007 |
| Strömsön Vesi- ja jätehuolto Oy | Construction | 2007 |
| Strömsön Yhteyssatama Oy | Real estate | 2008 |
| Sustainabuild Oy | Professional & scientific | 2020 |
| Swift Solutions öppet bolag | Information & communication | 2020 |
| Sydbevakning Ab | Administrative & support | 1993 |
| Sydspetsens Glas & Bygg Ab Oy | Construction | 2020 |
| Sydvästdata AB | Wholesale & retail | 1989 |
| Sydweb Ab | Information & communication | 2004 |
| Södergårds Terapi & Utbildning Ab | Health & social care | 2020 |
| Södra Leksvalls vattenandelslag | Water & waste | 2020 |
| Södra vikens bokföring AB | Professional & scientific | 1991 |
| T.Sandberg AB OY | Construction | 2025 |
| TL Pipe Ab | Construction | 2018 |
| Tn-Bryggan AB | Manufacturing | 2015 |
| TP Vision Europe B.V.,Suomen sivuliike | Wholesale & retail | 2014 |
| TREM öppet bolag | Construction | 1999 |
| TS All for Your business Ab Oy | Professional & scientific | 1995 |
| TS Byggservice Ab | Construction | 2026 |
| Taksipalvelu Eri Oy | Transport & logistics | 2026 |
| Taloveto Oy | Real estate | 2022 |
| Tammet Oy | Manufacturing | 1948 |
| Tammisaaren Autokauppakiinteistö Oy | Real estate | 1978 |
| Tammisaaren Harjuhalli Oy | Real estate | 1975 |
| Tammisaaren Kaupunginhotelli Oy | Hospitality | 1997 |
| Tammisaaren Marine Oy | Hospitality | 1991 |