| SS-Business Oy | Wholesale & retail | 2002 |
| SSC GROUP avoin yhtiö | Construction | 2013 |
| SSN-Holding Oy | Professional & scientific | 2026 |
| SSN-Rentals Oy | Administrative & support | 2026 |
| STH Kiinteistö Oy Mäntysuonkatu 4 | Real estate | 2020 |
| STH-Cargo Oy | Transport & logistics | 2021 |
| STH-Holding Oy | Administrative & support | 2021 |
| STH-Service Oy | Manufacturing | 2011 |
| STV Palvelut OY | Construction | 2020 |
| Suomen Pelikauppa OY | Wholesale & retail | 2012 |
| SVN Kiinteistöt Oy | Real estate | 2019 |
| Sweet Karelia OY | Professional & scientific | 2019 |
| Saani Avoin yhtiö | Hospitality | 2015 |
| Saaren Siivouspalvelut Oy | Administrative & support | 2024 |
| Safar Oy | Financial services | 1990 |
| Saimaa City Apartments Hotel Oy | Hospitality | 2008 |
| Saimaa Coaching Oy | Administrative & support | 2022 |
| Saimaa Express Oy | Transport & logistics | 1993 |
| Saimaa Finsky Vodka Oy Ltd | Manufacturing | 2021 |
| Saimaa Group Oy | Construction | 2011 |
| Saimaa Housing Oy | Hospitality | 2009 |
| Saimaa Laituri Oy | Transport & logistics | 2013 |
| Saimaa Rentals Oy | Construction | 2004 |
| Saimaa Warehouse OY | Professional & scientific | 2023 |
| Saimaan Asuntopalvelu Oy | Real estate | 2023 |
| Saimaan Autokatsastus Oy | Professional & scientific | 2015 |
| Saimaan Deli Oy | Hospitality | 2017 |
| Saimaan Digicontrol Oy | Construction | 2009 |
| Saimaan Eristys Oy | Construction | 2013 |
| Saimaan Gasti Oy | Transport & logistics | 2016 |
| Saimaan Helmi Oy | Hospitality | 2000 |
| Saimaan Honkaranta Oy | Real estate | 2001 |
| Saimaan Huoltopalvelu Oy | Other services | 1976 |
| Saimaan Iloiset Lauttapojat Oy | Arts & recreation | 2022 |
| Saimaan Kirja ja Levy Kommandiittiyhtiö | Wholesale & retail | 1984 |
| Saimaan Kodit Oy | Real estate | 2016 |
| Saimaan Kotiapu Oy | Health & social care | 2017 |
| Saimaan Käyttöteräs Oy | Wholesale & retail | 2005 |
| Saimaan LP Oy | Construction | 2025 |
| Saimaan Liikekiinteistöt Oy | Real estate | 1992 |
| Saimaan Lukkoturva Oy | Wholesale & retail | 2011 |
| Saimaan Matkaverkko Oy | Administrative & support | 1996 |
| Saimaan Nostolaitteet Oy | Wholesale & retail | 2017 |
| Saimaan Optiikka Oy | Wholesale & retail | 2002 |
| Saimaan Palveluverkko Oy | Real estate | 2013 |
| Saimaan Polttoaine Oy | Wholesale & retail | 1994 |
| Saimaan Rakennuspalvelu Oy | Construction | 2022 |
| Saimaan Rengas Oy | Wholesale & retail | 2012 |
| Saimaan Sammutinhuolto Oy | Manufacturing | 2003 |
| Saimaan Saneeraus ja Sähkö oy | Construction | 2019 |
| Saimaan Sisäilma Oy | Administrative & support | 2004 |
| Saimaan Sähkäri Avoin Yhtiö | Construction | 1999 |
| Saimaan Sähköapu Oy | Construction | 1998 |
| Saimaan Taimi Oy | Agriculture & fishing | 2022 |
| Saimaan Takkakeskus Oy | Wholesale & retail | 2006 |
| Saimaan Talovaruste Oy | Wholesale & retail | 2018 |
| Saimaan Teollisuuspalvelut Oy | Manufacturing | 1998 |
| Saimaan Trukkityö Oy | Transport & logistics | 1992 |
| Saimaan Tukipalvelut Oy | Administrative & support | 1953 |
| Saimaan Työpalvelu Oy | Administrative & support | 2013 |
| Saimaan Työtarvike Oy | Wholesale & retail | 2021 |
| Saimaan Uistin Ky | Manufacturing | 1985 |
| Saimaan Vaneri Ky | Manufacturing | 1981 |
| Saimaan Web-Palvelut Oy | Professional & scientific | 2021 |
| Saimaan arkihuolto Oy | Administrative & support | 2025 |
| Saimaan kiinteistöyhtiö Oy | Administrative & support | 2024 |
| Saimaan puhdistuspalvelu Oy | Water & waste | 2003 |
| Saimaan seutujen Opisto-osakeyhtiö | Other services | 1963 |
| Saimaan taksipalvelu Oy | Transport & logistics | 2024 |
| Saimaan urakointi oy | Transport & logistics | 2023 |
| Saimaanharjun Service Oy | Real estate | 2007 |
| Saimaprint Oy | Professional & scientific | 2013 |
| Saimensis Management Oy | Professional & scientific | 2026 |
| Sairaanhoito Saimaa Oy | Health & social care | 2018 |
| Sairaankuljetus Heimo Ruokonen Ky | Health & social care | 1985 |
| Saivu Capital Oy | Real estate | 2019 |
| Sakuratarha Oy | Hospitality | 2024 |
| Salhar avoin yhtiö | Hospitality | 2012 |
| Salon Leena Kolari Oy | Other services | 1981 |
| Salon8 Oy | Other services | 2015 |
| Salonen Capital Oy | Wholesale & retail | 2014 |
| Salpatek Oy | Administrative & support | 2007 |
| SamiPetteri Oy | Construction | 2023 |
| Sammonlahden autokorjaamo Oy | Manufacturing | 2016 |
| Sammut Software Oy | Information & communication | 2015 |
| SamppaWorks Oy | Construction | 2025 |
| Samra Oy | Transport & logistics | 1981 |
| Saneeraus Eloranta Oy | Construction | 2018 |
| Saneeraus J. Liikka Oy | Construction | 1995 |
| Saneeraus ja Asennus Pöllänen Oy | Construction | 2018 |
| Saneeraus ja Maalaus Raappana Oy | Construction | 1991 |
| Santa Finn Kolme Oy | Professional & scientific | 1990 |
| Sanura Suomi Oy | Wholesale & retail | 1986 |
| Sapeko Group Oy | Administrative & support | 2020 |
| Sarvi Steel Oy | Administrative & support | 2025 |
| Sataman Antiikki & Design Oy | Wholesale & retail | 2009 |
| Sataman Loiste Oy | Wholesale & retail | 2010 |
| Sataman Pitsi Oy | Hospitality | 2020 |
| Satumainen Lapsuus Oy | Education | 2013 |
| Savitaipaleen Nikkilä Oy | Construction | 1992 |