| Salkor Oy | Other services | 2025 |
| Salmon Trio Oy | Manufacturing | 2021 |
| Salo City-Flats Oy | Real estate | 1996 |
| Salon Marjo Ahola Oy | Other services | 2005 |
| Salon Marjo Ahola Project oy | Real estate | 1998 |
| SamGra Oy | Administrative & support | 1993 |
| SamHile Oy | Real estate | 2014 |
| Sami Natri Oy | Hospitality | 1997 |
| Sammallahti Trading Oy | Transport & logistics | 2020 |
| Samuli Kalliosalo Oy | Transport & logistics | 2012 |
| Sanapiste Oy | Administrative & support | 2024 |
| Santenig Oy | Real estate | 1984 |
| Sarey Group Oy Ab | Professional & scientific | 2023 |
| Sargo Oy Ab | Manufacturing | 1970 |
| Sari and the Kids Oy | Financial services | 2023 |
| Sarmit Group Oy | Administrative & support | 2016 |
| Satanolla Oy | Professional & scientific | 2011 |
| Savari Management Oy | Wholesale & retail | 2026 |
| Savoja Oy | Wholesale & retail | 2018 |
| Savuseppä Oy | Manufacturing | 2020 |
| Sawelding Oy | Manufacturing | 2025 |
| Scantoshop Oy Ab | Manufacturing | 2019 |
| SePiTa oy | Transport & logistics | 2018 |
| Seafood Finland Oy | Wholesale & retail | 2003 |
| SebTom Oy | Real estate | 2017 |
| Seimec Service Oy | Manufacturing | 2014 |
| Senra Group Oy | Construction | 2016 |
| SepinSaneeraus Oy | Construction | 2014 |
| Sepitex Oy | Real estate | 1980 |
| Seppälän Parturi-Kampaamo, Avoin yhtiö | Other services | 1979 |
| Seripaino Jokela Oy | Manufacturing | 1995 |
| ServMet Oy | Professional & scientific | 2018 |
| Setrak Oy | Real estate | 1994 |
| Seven Foods Oy | Hospitality | 2014 |
| Shams group Oy | Hospitality | 2025 |
| ShineHouse Oy | Administrative & support | 2010 |
| Shun He Oy | Hospitality | 2025 |
| Sigma Algebra Ltd Oy | Professional & scientific | 2024 |
| SignPrint Markkinointi Oy | Manufacturing | 2011 |
| Siivouspalvelu Lassi Oy | Administrative & support | 1991 |
| Siivouspalvelu Lukkarila Oy | Administrative & support | 2004 |
| Siivouspalvelu Soneki Avoin Yhtiö | Administrative & support | 2017 |
| Siivouspalvelu Syri Oy | Administrative & support | 2021 |
| Sijoitusyhtiö Tervola Oy | Real estate | 2001 |
| Sikapatti Oy | Energy | 2024 |
| Siltamarkka Oy | Financial services | 2022 |
| Silverphone Oy | Wholesale & retail | 2022 |
| Silverstone Bay Logistics Oy | Transport & logistics | 2015 |
| Simodeus Invest Oy | Wholesale & retail | 1991 |
| Simodeus Oy | Arts & recreation | 1995 |
| Singh's flavique oy | Hospitality | 2025 |
| Sisu Siivous Oy | Administrative & support | 2023 |
| Sisustus ja Lahjaliike Zinna Oy | Wholesale & retail | 2016 |
| Sisustuspaletti Oy | Professional & scientific | 2015 |
| Sisärakenne Kokkola Oy | Construction | 2016 |
| Skogin Tienparannus Oy Ab | Construction | 1980 |
| Slow Events Oy | Arts & recreation | 2024 |
| Smart Siivous Oy | Administrative & support | 2010 |
| Smart rental Oy | Administrative & support | 2020 |
| Smiling Oy | Health & social care | 2025 |
| Smokey Road Diner & Bar Oy | Hospitality | 2026 |
| Snellpirtti Oy | Real estate | 1979 |
| SocEnter Consulting Oy | Administrative & support | 2018 |
| Social Group Oy | Hospitality | 2025 |
| Sofik Oy | Professional & scientific | 2025 |
| Softwave Ohjelmistot Oy | Information & communication | 2003 |
| Sokojan Autohuolto Oy | Other services | 2025 |
| Sokojan Helmi Oy | Real estate | 2023 |
| Solmu Design Avoin yhtiö | Professional & scientific | 2010 |
| Solnix Persienn och Markis Ab | Manufacturing | 2023 |
| Sopiva Isännöinti Oy | Real estate | 2024 |
| Sorasan Oy | Construction | 2018 |
| Sourcewind Capital Oy | Financial services | 2017 |
| Souza-Enroth Trading, Sales & Consulting avoin yhtiö | Wholesale & retail | 2010 |
| Sports Club ROK Oy | Arts & recreation | 2016 |
| Stailer Oy | Real estate | 1981 |
| Stall Hilltorp,öppet bolag | Arts & recreation | 2002 |
| Stiderai Oy | Manufacturing | 1998 |
| Stigi Oy | Professional & scientific | 2024 |
| Storbacka Holding Ab | Wholesale & retail | 1975 |
| Storbjörk Solutions Oy | Financial services | 2024 |
| Storen Väri Oy | Wholesale & retail | 1999 |
| Storfors Elektriska Kraftcentral A/B | Professional & scientific | 1915 |
| Studio Frekvens Oy | Professional & scientific | 2021 |
| Studio M.S muhis Oy | Other services | 2024 |
| Studio Tomi Yrjänä Oy | Other services | 2012 |
| Studio Wiik, öppet bolag | Professional & scientific | 1981 |
| Studiopop Finland Oy | Information & communication | 2000 |
| Suffi Oy | Arts & recreation | 2023 |
| Sukkamafia Oy | Wholesale & retail | 2025 |
| Sun Story Oy | Real estate | 1990 |
| Sun and Snow Weddings Oy | Administrative & support | 2013 |
| SunGym Oy | Arts & recreation | 2021 |
| Sunami Oy | Arts & recreation | 2019 |
| Sunerva Oy | Arts & recreation | 2024 |
| Suntti Running Events Oy | Arts & recreation | 2025 |
| Suomen KeittiöKaluste Oy | Wholesale & retail | 2015 |
| Suomen Kuormalavat Oy | Wholesale & retail | 2009 |
| Suomen Robottimaalaus Oy | Manufacturing | 2024 |
| Suomen Tekstiilitukku Oy | Wholesale & retail | 1992 |