| MJP Holding Oy | Professional & scientific | 2023 |
| MK Asennustekniikka Oy | Manufacturing | 2022 |
| MK Automyynti Oy | Wholesale & retail | 2023 |
| MK Petäjäniemi Oy | Wholesale & retail | 2021 |
| MK Puhdistus palvelu Oy | Administrative & support | 2025 |
| MK Talotekniikka Oy | Construction | 2022 |
| MKM Design Oy | Professional & scientific | 2021 |
| MKOy Group Oy | Administrative & support | 2025 |
| ML Kansityö Oy | Other services | 2016 |
| MM Autopalvelut Oy | Other services | 2015 |
| MN Coating Oy | Construction | 2020 |
| MN Group Oy | Construction | 2013 |
| Mo&La OY | Other services | 2023 |
| MOJAVE Holding Oy | Professional & scientific | 2026 |
| MP-Invest Ky | Real estate | 1992 |
| MP-Roskaton Oy | Water & waste | 1996 |
| MPA Maalaus Oy | Other services | 2023 |
| MPEK Oy | Administrative & support | 2025 |
| MPI-Family Holding Oy | Financial services | 2024 |
| MPP Group Oy | Financial services | 2022 |
| MSS-Kuljetus KY | Transport & logistics | 2010 |
| MY-Insinöörit Group Oy | Professional & scientific | 2020 |
| MY-Insinöörit Oy | Construction | 2018 |
| Maahipuu Oy | Construction | 2020 |
| Maakastari Ky | Construction | 1990 |
| Maalaus- ja tasoitetyö J. Tornberg Oy | Construction | 2001 |
| Maalaus- ja tasoitetyöt J. Sinkkonen Oy | Construction | 2005 |
| Maalausliike Jaakko Rötkönen Ky | Construction | 1984 |
| Maalausliike Kalervo Sinkkonen Ky | Construction | 1982 |
| Maalausliike Laitila Oy | Construction | 1995 |
| Maalaustyöt Kari Kinnunen Oy | Construction | 1990 |
| Maalaustyöt MP Oy | Construction | 2025 |
| Maankäyttö Pesonen Oy | Professional & scientific | 2021 |
| Maanrakennus Heikkilä Oy | Construction | 2012 |
| Maanrakennus S. Kursula Oy | Construction | 2017 |
| Maansiirtoliike Kemppe Oy | Construction | 1995 |
| Maansiirtoliike Koivula Ky | Construction | 1983 |
| Maansiirtoliike Raimo Heimo Oy | Construction | 1991 |
| Maansiirtoliike S.Välitalo Ky | Construction | 1991 |
| Maansiirtoliike Yrjänheikki Oy | Construction | 1989 |
| MadBoy Audio International Oy | Arts & recreation | 2009 |
| Madagas Oy | Wholesale & retail | 2024 |
| Mah Group Oy | Financial services | 2021 |
| Mahicap Oy | Administrative & support | 2007 |
| Mahla-talot Oy | Construction | 2014 |
| Mahtte Oy | Construction | 2025 |
| Maikki Vaara Design | Administrative & support | 2025 |
| Maikkula Welding & Rigging Oy | Manufacturing | 2019 |
| Mainoa DESIGN SHOP Ky | Professional & scientific | 2010 |
| Mainoa Estates Oy | Real estate | 2026 |
| Mainos Harila Oy | Professional & scientific | 2005 |
| Mainostoimisto Kiuas Oy | Professional & scientific | 1997 |
| Mainostoimisto Puisto Oy | Professional & scientific | 2008 |
| Maintcon Oy | Information & communication | 2020 |
| Maire Isoviita Ky | Wholesale & retail | 1993 |
| Majaika Oy | Hospitality | 2017 |
| Majou Oy | Construction | 2017 |
| Makeekauppa Oy | Wholesale & retail | 2017 |
| Mandragora Oy | Wholesale & retail | 2021 |
| Mapira Oy | Construction | 2019 |
| Marge oy | Construction | 2018 |
| Marina Bistro & Lounge Oy | Real estate | 2026 |
| Markkinointipalvelu Tuovinen Oy | Professional & scientific | 1996 |
| Markku Eskola Ky | Wholesale & retail | 1990 |
| Markku Iljina GeoConsulting Oy | Professional & scientific | 2012 |
| Marko A Tervaniemi Consulting Oy | Professional & scientific | 2011 |
| Marmelli Oy | Administrative & support | 2020 |
| Marrasjärven konetyö Oy | Administrative & support | 2023 |
| Marrent Oy | Administrative & support | 2000 |
| Martti Vainio Ky | Construction | 1998 |
| Marttiini Metal Oy | Manufacturing | 2020 |
| Marttiini Yhtymä Oy | Real estate | 2020 |
| Masser Oy | Manufacturing | 1987 |
| Massi Auto Oy | Education | 2002 |
| Matkanautti Oy | Transport & logistics | 2026 |
| Matti H. Vierimaa Oy | Professional & scientific | 2005 |
| Matti Sarkkinen Oy | Financial services | 2021 |
| Mattira Oy | Health & social care | 2007 |
| Mattoasennus O. Ojala Oy | Construction | 1997 |
| Mattoparatiisi Oy | Wholesale & retail | 2024 |
| Mawson Oy | Mining & quarrying | 2011 |
| Maxam Suomi Oy | Manufacturing | 2007 |
| Med Eeros Major Oy | Health & social care | 2023 |
| Medirak Oy | Professional & scientific | 2026 |
| Medvis Oy | Wholesale & retail | 2004 |
| Megastaff Holding Oy | Other services | 2021 |
| Mehmet Oba Oy | Wholesale & retail | 2025 |
| Mehtä-Hyvönen Oy | Agriculture & fishing | 2023 |
| Mejän tiimi Oy | Health & social care | 2020 |
| Mellalux Resort Oy | Hospitality | 2025 |
| Memorycraft Studios Oy | Professional & scientific | 2025 |
| Metsäkiinteistöt Hannu Tervo Lkv Oy | Real estate | 1994 |
| Metsäkone Sarajärvi Oy | Agriculture & fishing | 1992 |
| Mevi Group Oy | Financial services | 2023 |
| Mianel Oy | Professional & scientific | 2026 |
| Midnight Academy Oy | Education | 2018 |
| Miehet Pihalla avoin yhtiö | Construction | 2008 |
| Mieka Oy | Health & social care | 2017 |
| Miekojärven Helmi Oy | Hospitality | 2024 |
| MielenAsia Oy | Health & social care | 2023 |