| Mikaso Liikenne Oy | Transport & logistics | 2016 |
| MikeysCarParts Oy | Wholesale & retail | 2026 |
| Milla Suominen Oy | Real estate | 2019 |
| Mimarko Oy | Wholesale & retail | 2009 |
| Mimosan Aito Oy | Hospitality | 2018 |
| Mipamax Oy | Real estate | 2023 |
| Modric Oy | Wholesale & retail | 2023 |
| Modulepod Oy | Manufacturing | 2026 |
| Molva Oy | Other services | 1989 |
| Monelle Oy | Administrative & support | 2003 |
| Moniasennus ATTEK Oy | Construction | 2007 |
| Monipalvelu Pukkila & Hyypiä Oy | Transport & logistics | 2022 |
| Monitoimi Konsultit Oy | Health & social care | 1990 |
| Monume Oy | Professional & scientific | 2023 |
| More Than Feeling Oy | Other services | 2025 |
| Motoworks Finland Oy | Other services | 2010 |
| Muotitalo Hokkanen Oy | Wholesale & retail | 1988 |
| Muotti & Injektointi Pe-To Oy | Wholesale & retail | 2009 |
| Musketti Oy | Real estate | 2020 |
| Muutot ja Kuljetukset Heikki Hietala Oy | Transport & logistics | 1995 |
| Mykkä Hiihtäjä Oy | Hospitality | 2016 |
| Mäntyovi Mielonen Oy | Manufacturing | 1983 |
| N.H Whistle Oy | Arts & recreation | 2020 |
| N.S.F. Nordic Sports Finland Oy | Wholesale & retail | 1994 |
| NIPATU Oy | Manufacturing | 2026 |
| NK Lehtoniemi Oy | Administrative & support | 2019 |
| Norad Service OY | Manufacturing | 2020 |
| Novoc OY | Real estate | 2007 |
| NSC Group Oy | Health & social care | 2021 |
| Nallewear clothing Oy | Wholesale & retail | 2019 |
| Neliöt kodiksi Oy | Real estate | 2021 |
| Neliövälitys Oy LKV | Real estate | 2010 |
| Niilon Invest Oy | Real estate | 1990 |
| Niinitalo Oy | Construction | 2023 |
| Nikadent Oy | Health & social care | 2026 |
| Nilor Oy | Financial services | 1995 |
| Nirvana Lifestyle Oy | Wholesale & retail | 2008 |
| Nole Studios Oy | Professional & scientific | 2024 |
| Nolo hyytyy Oy | Arts & recreation | 2019 |
| Nordic Auto Import Oy | Wholesale & retail | 2025 |
| Nordic Design Solutions Oy | Wholesale & retail | 2023 |
| Nordic Gloves Oy | Wholesale & retail | 2012 |
| Nordic Logistics & Ferry Service Oy | Transport & logistics | 2019 |
| Nordic Welfare Oy | Administrative & support | 2021 |
| Nordvahl Holding Oy | Financial services | 2025 |
| Nuanic Oy | Manufacturing | 2013 |
| Nummi Kiinteistöt Oy | Real estate | 2003 |
| Nuorten Startti Oy | Administrative & support | 2024 |
| Nykysiivous Oy | Administrative & support | 1973 |
| Nyt Liikkeelle Oy | Education | 2026 |
| O.J.-Vesitorni Oy | Real estate | 2024 |
| OAW Holding Oy | Wholesale & retail | 1965 |
| OK-Media Oy | Manufacturing | 1995 |
| OT Automaatio Oy | Construction | 1997 |
| OTH-Taksi Oy | Transport & logistics | 2025 |
| Oylab OY | Manufacturing | 2025 |
| Oil Team Oy | Arts & recreation | 2022 |
| Ojamaan-Niinimäen vesihuolto-osuuskunta | Water & waste | 2004 |
| Olavin Kellari Oy | Manufacturing | 2021 |
| Oliivipuu Oy | Financial services | 2025 |
| Ollikka-Invest Oy | Real estate | 1995 |
| Ompelu-Ateljee Ajan Ommel Ky | Manufacturing | 1996 |
| Ompelukoneliike O&J Niemelä Ky | Wholesale & retail | 1997 |
| On Sum Oy | Hospitality | 2018 |
| One Sweet Creation Oy | Wholesale & retail | 2020 |
| Onevisio Oy | Information & communication | 2007 |
| Onkisalon Hurja Oy | Real estate | 2006 |
| Opeko Rakennus Oy | Construction | 2008 |
| Optimitilit avoin yhtiö | Professional & scientific | 2011 |
| Optiot Hotinen Oy | Financial services | 1998 |
| Oriental Aurora Investment Oy | Wholesale & retail | 2018 |
| Osmon Pienkone Oy | Wholesale & retail | 1996 |
| Osuuskunta Monitoimiseniorit, Kouvola | Administrative & support | 2014 |
| Osuuskunta Tietokymi | Information & communication | 2002 |
| Oy Acaris Ab | Health & social care | 2011 |
| Oy AlterEco Technologies Ltd | Other services | 2013 |
| Oy Atlas-Invest Ab | Financial services | 2003 |
| Oy Atlas-Metalli Ab | Manufacturing | 1992 |
| Oy DP Consulting Europe Ltd | Wholesale & retail | 2015 |
| Oy Envener Ltd | Construction | 2011 |
| Oy Kausala Wood Ltd | Manufacturing | 2009 |
| Oy Nanguvilla | Real estate | 1973 |
| Oy PR-Hallinto Ab | Professional & scientific | 1992 |
| Oy Rauli Lönnfors Ab | Financial services | 1981 |
| Oy Scan-Zhul Ab | Wholesale & retail | 1995 |
| Oy Tero Hurtta Corporation | Financial services | 1989 |
| Oy Tikkanen Music Ltd | Information & communication | 2012 |
| Oy Westermarck Ab | Wholesale & retail | 1987 |
| P K Henttonen Oy | Professional & scientific | 2021 |
| P.P. Fashion Ky | Wholesale & retail | 2012 |
| PEMA Development Oy | Real estate | 2007 |
| PH-Tuote Ky | Professional & scientific | 1986 |
| PHE-Rakennus Ky | Construction | 1998 |
| PHTuo. Invest Oy | Construction | 2013 |
| PJL-Group Oy | Real estate | 2025 |
| PK-Muovi Oy | Manufacturing | 2007 |
| PMA Power Oy | Professional & scientific | 2025 |
| PMK Autokorjaus Avoin yhtiö | Other services | 2009 |
| POB Group Oy | Information & communication | 2024 |
| PP Rakennuskonsultointi Oy | Professional & scientific | 2017 |