| MFD Holding Oy | Financial services | 2025 |
| MJK Rahti Oy | Transport & logistics | 2026 |
| MJT-Multiservice Oy | Real estate | 1994 |
| MK-Kiinteistöt Oy | Real estate | 2020 |
| ML Caravan Oy | Wholesale & retail | 2006 |
| MP-Myynti Oy | Real estate | 2022 |
| MPB Kiinteistöt Oy | Real estate | 2011 |
| MSD Kiinteistöt Oy | Real estate | 2011 |
| MSR Rakennuspalvelu Oy | Construction | 2022 |
| MT Karppinen Group Oy | Health & social care | 2025 |
| MVL-Systems Niemi Oy | Manufacturing | 2014 |
| Maa- ja lumiurakointi Jouko Mäkelä Ky | Administrative & support | 1981 |
| Maalaus L & M Oy | Construction | 2017 |
| Maalaus ja Tasoite Veljekset Järvinen Oy | Construction | 1989 |
| Maalausliike J. Kiviniemi Ky | | 1987 |
| Maalausliike Repton Oy | Construction | 2002 |
| Maanrakennus Toni Lilja Oy | Construction | 2003 |
| Maansiirto Clewer Oy | Construction | 1997 |
| Maasemarket Oy | Wholesale & retail | 2025 |
| Maatila-Tili Juhani Saharinen Ky | Professional & scientific | 1989 |
| Maberak Oy | Construction | 2025 |
| Maijala Fashion Ky | Wholesale & retail | 2020 |
| Mainos Kaiser Oy | Manufacturing | 1991 |
| Majafast Oy | Other services | 1975 |
| Makutehdas Oy | Hospitality | 2013 |
| Malfix Oy | Construction | 2020 |
| Malluskiinteistöt Oy | Real estate | 2016 |
| Maria Drockila Oy | Manufacturing | 1993 |
| Markku Matikainen Oy | Agriculture & fishing | 1983 |
| Marko Hyökki Oy | Construction | 2025 |
| Marte Oy | Construction | 2006 |
| MaterialOps Oy | Wholesale & retail | 2025 |
| Maukas Hetki Oy | Hospitality | 2016 |
| Maxcap Oy | Real estate | 2004 |
| Maxiestate Oy | Real estate | 2013 |
| Maxihalli Oy | Real estate | 2015 |
| Maxirakennus Oy | Construction | 2011 |
| Megalattiat Oy | Construction | 2002 |
| Mesakon Oy | Construction | 2024 |
| Metsä kasvu Ky | Agriculture & fishing | 2014 |
| Metsäpalvelu Pitopuu Oy | Agriculture & fishing | 2021 |
| MiHi Palvelut Avoin yhtiö | Wholesale & retail | 2017 |
| Mikko Kaasinen Oy | Transport & logistics | 2009 |
| Mildomas Oy | Professional & scientific | 2025 |
| Mione Oy | Construction | 2006 |
| Mirakoru Oy | Wholesale & retail | 2024 |
| Motopalvelu Niemitalo Oy | Wholesale & retail | 1996 |
| Multasmäki Oy | Real estate | 1993 |
| Muotoilutoimisto Muki Osk | Professional & scientific | 2017 |
| Musculus Oy | Health & social care | 1981 |
| Mutkamusic Oy | Professional & scientific | 1983 |
| Mydeco Oy | Construction | 1996 |
| Mäki Kiinteistöt Oy | Real estate | 1989 |
| NA Capital Oy | Professional & scientific | 2021 |
| Neon Meri Oy | Professional & scientific | 2001 |
| Nesco Invest Oy | Professional & scientific | 2011 |
| Niinan Kahvila Kuumakuppi Oy | Hospitality | 2020 |
| Nikke Areena Oy | Real estate | 2011 |
| Nipinnapin Oy | Construction | 2026 |
| NordZence Oy | Professional & scientific | 2025 |
| Nordic Gate for Food Oy | Wholesale & retail | 2019 |
| Nordic Medicine and Wellness Oy | Education | 2016 |
| Nordic Piling Solutions Oy | Construction | 2021 |
| Notariaattiexpertti Toivoset Oy | Financial services | 1988 |
| Nummelan betonivalimo Oy | Manufacturing | 1973 |
| Nummi Steel Oy | Manufacturing | 2022 |
| OK-Hirsitalomyynti Oy | Wholesale & retail | 1993 |
| Okeko OY | Construction | 2024 |
| OKH-Palvelut Oy | Administrative & support | 2023 |
| OSRENT Oy | Other services | 2022 |
| Okatek Oy | Other services | 2015 |
| OneFX Oy | Information & communication | 2014 |
| Onesys Oy | Professional & scientific | 1990 |
| Onetiki Oy | Professional & scientific | 2019 |
| Onniasunnot Oy | Real estate | 2019 |
| Optitekno Oy | Wholesale & retail | 1993 |
| OrdoNovus Ky | Real estate | 2009 |
| Orfer Oy | Manufacturing | 1970 |
| Orfer Services Oy | Manufacturing | 1980 |
| OrigoHuolto Oy | Administrative & support | 2015 |
| Orima-Tuote Oy | Manufacturing | 1994 |
| Orimattilan Asunnot Oy | Real estate | 1991 |
| Orimattilan Isännöintipalvelu Miran Oy | Real estate | 2024 |
| Orimattilan Kello Avoin yhtiö | | 1965 |
| Orimattilan Kivi Oy | Manufacturing | 1993 |
| Orimattilan Kouru ja Tikas Oy | Construction | 2000 |
| Orimattilan La Casa Oy | Hospitality | 2020 |
| Orimattilan Lämpö Oy | Energy | 1983 |
| Orimattilan Lämpöasennus Oy | Construction | 1993 |
| Orimattilan Pieni Kultapuoti Oy | Wholesale & retail | 2007 |
| Orimattilan Putkityö Oy | Construction | 1958 |
| Orimattilan Siivouspalvelu Ky | Administrative & support | 1984 |
| Orimattilan Sähköpalvelu Oy | Construction | 1979 |
| Orimattilan Taksikeskus Oy | Transport & logistics | 1976 |
| Orimattilan Urheilu ja Kone Oy | Wholesale & retail | 1978 |
| Orimattilan Vartiointikeskus Oy | Administrative & support | 1993 |
| Orimattilan Vesi Oy | Real estate | 1993 |
| Orimattilan Viljasiilot Oy | Transport & logistics | 2014 |
| Orimattilan Yrityskiinteistöt Oy | Real estate | 2000 |
| Orimattilan Yrityspalvelu Ky | Professional & scientific | 1995 |