| Risto Pitkänen Oy | Construction | 2014 |
| River Oy | Financial services | 1989 |
| RobR oy | Construction | 2018 |
| Rokokiili Invest Oy | Wholesale & retail | 1966 |
| Roksu Oy | Wholesale & retail | 2022 |
| Rollikka Oy | Wholesale & retail | 2010 |
| Romppu Oy | Agriculture & fishing | 2013 |
| Rompun kone ja Metsäpalvelu Oy | Agriculture & fishing | 2000 |
| Romuliiteri OY | Other services | 2020 |
| Rosalex Group Oy | Real estate | 2010 |
| Roth Visions Oy | Construction | 2026 |
| Rotoco Oy | Real estate | 2020 |
| Roven Digital Oy | Information & communication | 2025 |
| Royal Interior Oy | Professional & scientific | 1985 |
| Royal Kalusteet Oy | Manufacturing | 1990 |
| Rudolfin Keidas Oy | Agriculture & fishing | 1993 |
| Ryösä Arkkitehdit Oy | Professional & scientific | 2021 |
| Rämsöön Hirsi Oy | Manufacturing | 2021 |
| SAJ Kodit Oy | Real estate | 2016 |
| SCWG Group Oy | Professional & scientific | 2023 |
| SF Rakentava Oy | Construction | 2000 |
| SK-Vakka Oy | Real estate | 2025 |
| SK-Vuokrakiinteistöt Oy | Real estate | 2025 |
| SL-Nuohous Oy | Construction | 2025 |
| SMK Consulting Oy | Professional & scientific | 2024 |
| SP Polymeeri Oy | Manufacturing | 2019 |
| STR Nordic Oy | Professional & scientific | 2018 |
| STS-Invest Oy | Construction | 1989 |
| SYSE Oy | Professional & scientific | 2013 |
| Sales League Oy | Financial services | 2022 |
| Salesmans Legacy Oy | Professional & scientific | 1996 |
| Salmi Oy | Manufacturing | 1971 |
| Salmin kylän vesiosuuskunta | Water & waste | 2023 |
| Salpuu Oy | Manufacturing | 2024 |
| Sami Koivisto Ky | Transport & logistics | 1999 |
| Sammaljoen vesiosuuskunta | Water & waste | 1989 |
| Sanderm Oy | Health & social care | 2021 |
| Sariko Oy | Administrative & support | 2013 |
| Sasmul Oy | Wholesale & retail | 2020 |
| Sastacon Oy | Professional & scientific | 2019 |
| Sastamalan Hyötyajoneuvohuolto Oy | Other services | 2011 |
| Sastamalan Kiinteistö- ja remonttiapu Oy | Construction | 2017 |
| Sastamalan Kiinteistöhuolto Oy | Administrative & support | 2019 |
| Sastamalan Kiinteistötekniikka Oy | Administrative & support | 1995 |
| Sastamalan Kodintekniikka Oy | Wholesale & retail | 2011 |
| Sastamalan Konehuolto Oy | Manufacturing | 2025 |
| Sastamalan Kotitalo Oy | Construction | 2022 |
| Sastamalan LVI Oy | Construction | 2012 |
| Sastamalan Lukko- ja Avainpalvelu SALPA Oy | Wholesale & retail | 2014 |
| Sastamalan Lämpö Oy | Energy | 1999 |
| Sastamalan Metsämulta Oy | Wholesale & retail | 2020 |
| Sastamalan Paitatehdas Oy | Manufacturing | 2013 |
| Sastamalan Peltityö Oy | Construction | 1995 |
| Sastamalan Putkityö Oy | Construction | 2002 |
| Sastamalan Pölkky Oy | Wholesale & retail | 2008 |
| Sastamalan Ruoka- ja Puhtauspalvelut Oy | Hospitality | 2011 |
| Sastamalan Taksikuljetus Oy | Transport & logistics | 2025 |
| Sastamalan Taksipalvelu Oy | Transport & logistics | 2020 |
| Sastamalan Turvatekniikka Ky | Administrative & support | 1999 |
| Sastamalan Työpalvelu OY | Agriculture & fishing | 2008 |
| Sastamalan Uimahalliyhtiö Oy | Other services | 2023 |
| Sastamalan Vuokratalot Oy | Real estate | 1990 |
| Sastamalan Wanha Pappila Avoin yhtiö | Administrative & support | 2006 |
| Sastamalan Ympäristöpalvelut Oy | Administrative & support | 2011 |
| Sastamalan edunvalvonta Oy | Health & social care | 2012 |
| Sastamalan export ja välitys oy | Wholesale & retail | 2020 |
| Sastamalan laskenta- ja tilipalvelu Oy | Administrative & support | 2020 |
| Sastamalan sijaishuoltopalvelut Oy | Health & social care | 2010 |
| Sastamarine KY | Administrative & support | 2009 |
| Sastarest Oy | Hospitality | 2015 |
| Sastatec Oy | Professional & scientific | 2014 |
| Sastmobil Oy | Administrative & support | 2009 |
| Sasvera Oy | Construction | 2019 |
| Satagroup Oy | Manufacturing | 2007 |
| Satapirkan Osuuspankki | Financial services | 1924 |
| Satapirkan Tuholaistorjunta Oy | Administrative & support | 2019 |
| Savelan Pelto Oy | Real estate | 2006 |
| Savelan Tila Oy | Agriculture & fishing | 1996 |
| Sekvest Oy | Professional & scientific | 2024 |
| Selkeen Kartano Oy | Hospitality | 2024 |
| Seppä T Oy | Transport & logistics | 2020 |
| Seppänen & Wigren Oy | Hospitality | 2020 |
| Serkukset Mäki-Soini Avoin yhtiö | Wholesale & retail | 2016 |
| Siipien suojassa woodwork Oy | Manufacturing | 2025 |
| Siivousaarre Ky | Administrative & support | 1986 |
| Sijoitus-Trio Oy | Financial services | 2005 |
| Sijoituselsi Oy | Financial services | 1989 |
| Sijoitusosakeyhtiö Siili | Financial services | 2016 |
| Sikapäänmäki Oy | Agriculture & fishing | 2025 |
| Silkkeri Oy | Manufacturing | 1974 |
| Silplast Oy | Wholesale & retail | 2005 |
| Siltalan Puu Oy | Manufacturing | 1988 |
| Sinervön Kauppa Oy | Wholesale & retail | 2002 |
| Sinolas Oy | Real estate | 2020 |
| Sirlog Oy | Transport & logistics | 2016 |
| Sisustus Torpo Oy | Manufacturing | 1999 |
| Sisustus-Seliina Ky | Professional & scientific | 2001 |
| Sisä-Suomen Ruoppaus Oy | Construction | 1989 |
| Sisältösepät Oy | Professional & scientific | 2025 |
| SkyBuilding Oy | Construction | 2018 |