| Superkodit Oy | Real estate | 2019 |
| Supermassive Black Box Oy | Professional & scientific | 2022 |
| Supernova Invest Oy | Financial services | 2009 |
| Superrakenne Oy | Real estate | 2016 |
| Superstandard Oy Ab | Professional & scientific | 2026 |
| Supervillain Capital Oy | Financial services | 2023 |
| Superäly Holding Oy | Financial services | 2024 |
| Supportti Oy | Professional & scientific | 2024 |
| Supro Oy | Construction | 2014 |
| SurSur Designs Oy | Wholesale & retail | 2012 |
| SurePartner Oy | Construction | 2019 |
| Surell Oy | Transport & logistics | 2026 |
| Surgify Medical Oy | Manufacturing | 2017 |
| Surgivision Oy | Health & social care | 2006 |
| Surina Oy | Professional & scientific | 1998 |
| Surya Oy | Hospitality | 2022 |
| Susa Tech Oy | Information & communication | 2025 |
| Susan Platinum Production Oy | Arts & recreation | 2019 |
| Susangyne Oy | Health & social care | 2025 |
| SuseLex Oy | Professional & scientific | 2025 |
| Susformation Oy | Professional & scientific | 2019 |
| Sushi Finland Oy | Administrative & support | 2017 |
| Sushi Konnichiwa Oy | Real estate | 2015 |
| Sushmita Oy | Hospitality | 2020 |
| SustDev Lab Oy | Professional & scientific | 2021 |
| Sustainable Forestry Finland Oy | Administrative & support | 2010 |
| Sustainable House Varsinais-Suomi Oy | Real estate | 2022 |
| Sustaineon 2 Oy | Professional & scientific | 2026 |
| Sustaineon Oy | Professional & scientific | 2024 |
| Sutina Consulting Oy | Professional & scientific | 2017 |
| Suuhygienisti Hannele Nyfors Oy | Health & social care | 2017 |
| Suuhygienistipalvelut Minna Johanna Oy | Health & social care | 2021 |
| Suunnittelukonttori Toinen Tila Oy | Professional & scientific | 2014 |
| Suunnittelukymppi OY | Professional & scientific | 1976 |
| Suunnittelutoimisto Axioma Oy | Professional & scientific | 1996 |
| Suunnittelutoimisto Imakebyro Oy | Professional & scientific | 1998 |
| Suunnittelutoimisto Lähde Oy | Professional & scientific | 2007 |
| Suunnittelutoimisto Malmari-Lampinen Kommandiittiyhtiö | Professional & scientific | 1979 |
| Suunnittelutoimisto Mami & Nero Oy | Professional & scientific | 2025 |
| Suunnittelutoimisto Reseptori Oy | Professional & scientific | 1999 |
| Suunnittelutoimisto SISUXI Oy | Professional & scientific | 2025 |
| Suunnittelutoimisto Soihtu Oy | Professional & scientific | 1989 |
| Suunnittelutoimisto Teo-Vision Oy | Real estate | 1994 |
| Suunnittelutoimisto Webit Oy | Information & communication | 2008 |
| Suunta Consulting Oy | Professional & scientific | 2021 |
| Suunta Digital Oy | Professional & scientific | 2025 |
| Suuntia Oy | Information & communication | 2014 |
| Suuntima Consulting Oy | Professional & scientific | 2022 |
| Suur-Helsingin Finanssi Oy | Financial services | 1979 |
| Suur-Helsingin Golf Oy | Arts & recreation | 1991 |
| Suur-Helsingin Markiisipalvelu Oy | Manufacturing | 1980 |
| Suur-Leppävaara LKV Oy | Real estate | 2019 |
| Suuraho Consulting Oy | Professional & scientific | 2023 |
| Suuret Avoin yhtiö | Wholesale & retail | 2007 |
| Suurhammas avoin yhtiö | Health & social care | 2010 |
| Suurpellon Rakennusprojektointi ja Kiinteistöhoito Oy | Professional & scientific | 2007 |
| Suurpellon jätehuolto Oy | Water & waste | 2008 |
| Suursuomen Muurimestarit Oy | Construction | 2007 |
| Suutari Juha Piiroinen Oy | Other services | 2023 |
| Suutari M. Laine Oy | Other services | 2007 |
| Suutari ja Avainpalvelu Kosonen & Puurunen avoin yhtiö | Other services | 2015 |
| Suvelan Fysikaalinen Hoitolaitos Oy | Health & social care | 1994 |
| Suvelan Huolto Oy | Administrative & support | 2026 |
| Suvi's Happy Oy | Financial services | 2019 |
| Suvisaari Systems Oy | Information & communication | 2009 |
| Suvisaariston Vesiosuuskunta-Sommarö Vattenandelslag | Water & waste | 1999 |
| Suzuki Deutschland GmbH, Suomen sivuliike | Wholesale & retail | 2001 |
| SvD Invest Oy | Financial services | 2006 |
| SvePatrak Oy | Construction | 2023 |
| Svedbergs Oy Ab | Wholesale & retail | 1992 |
| Sveins Consulting Oy | Health & social care | 2008 |
| Sveitsi Kiinteistörahasto Oy | Real estate | 2016 |
| Svennas Holding Oy | Financial services | 2021 |
| Svirak Group Oy | Construction | 2023 |
| Swan Capital Oy | Financial services | 2023 |
| Swan Holding Oy | Financial services | 2022 |
| SwanSound Holding Oy | Financial services | 2024 |
| Swantrade Oy | Real estate | 2017 |
| SweatShopBoys Oy | Wholesale & retail | 2026 |
| Sweet & Life Oy | Manufacturing | 2007 |
| Sweet & Salty Bakery Oy | Manufacturing | 2018 |
| Sweet Fruiti Oy | Wholesale & retail | 2015 |
| Sweety Ventures Oy | Professional & scientific | 2024 |
| Swesh Oy | Wholesale & retail | 2026 |
| Swiftgoo Oy | Information & communication | 2026 |
| Swinghill Oy Ab | Arts & recreation | 2000 |
| Sworkers Oy | Administrative & support | 2022 |
| Syafru Technologies Oy | Information & communication | 2026 |
| Sydholm Ab | Real estate | 1989 |
| Sydrad Oy | Health & social care | 2023 |
| Sydvesti Oy | Information & communication | 2014 |
| Sydämet Oy | Health & social care | 2020 |
| Sydänterveys PK Oy | Health & social care | 2017 |
| Sydänto Oy | Administrative & support | 2023 |
| Syikki Invest Oy | Professional & scientific | 2025 |
| Syke Consulting Oy | Health & social care | 2023 |
| Sylvester Korhonen oy | Wholesale & retail | 1973 |
| Sylvi Ventures Oy | Real estate | 2018 |
| Sylvian Oy | Professional & scientific | 2023 |
| Syma Solutions Oy | Professional & scientific | 2024 |