| Maalausliike Tuupanen Oy | Construction | 1978 |
| Maalausliike Uusimaa Oy | Construction | 2022 |
| Maalausliike Vilen & Syrjänen Oy | Construction | 2004 |
| Maalausliike Väriympyrä Oy | Administrative & support | 2019 |
| Maalausliike Wallenius Kommandiittiyhtiö | Construction | 1979 |
| Maalausmaa Oy | Construction | 2016 |
| Maalauspalvelu Mieliväri Oy | Construction | 2022 |
| Maalaustyö Koivuluoma Oy | Construction | 1984 |
| Maalausvalvonta Laeslehto Oy | Construction | 1981 |
| Maalausväline Simonen Oy | Manufacturing | 1960 |
| Maalikeisarit Oy | Construction | 2021 |
| Maalikuninkaat Oy | Construction | 2021 |
| Maalipotku Oy | Construction | 2025 |
| Maaliässät Oy | Construction | 2016 |
| Maalämpöhuoltokeskus Oy | Construction | 2015 |
| Maanrakennus A. Jääskeläinen Ky | Construction | 1970 |
| Maanrakennus Arto Kuikka Oy | Construction | 1995 |
| Maanrakennus Janne Sontag Oy | Construction | 2022 |
| Maanrakennus K. Lund Oy | Construction | 2024 |
| Maanrakennus Lauri Oy | Construction | 2025 |
| Maanrakennus MaKi Oy | Construction | 2018 |
| Maanrakennus Nikander Oy | Construction | 1997 |
| Maanrakennus Ranta Oy | Transport & logistics | 1992 |
| Maanrakennus Rummukainen Oy | Construction | 2025 |
| Maanrakennus S.V Korhonen Oy | Construction | 2017 |
| Maanrakennus TM OY | Construction | 2023 |
| Maanrakennuspalvelu Auttavat Kädet Oy | Construction | 2008 |
| Maansiirto K.T.Hiltunen Oy | Construction | 2025 |
| Maansiirto T. Koivisto Oy | Transport & logistics | 2023 |
| Maarakennus Jarmo Luostarinen Oy | Construction | 2014 |
| Maarakennus O. Ryhänen Oy | Construction | 1984 |
| Maarakennus Ollila Oy | Construction | 1987 |
| Maatukku Oy | Wholesale & retail | 2022 |
| Maavoima Oy | Transport & logistics | 2011 |
| Mabco Constructions SA, Suomen sivuliike | Construction | 2019 |
| Mac Madigan Oy | Financial services | 2024 |
| Mac Paananen Avoin yhtiö | Wholesale & retail | 2005 |
| Maces Cool & Building Oy | Construction | 2019 |
| Machinery Group Oy | Wholesale & retail | 1999 |
| Machinery Oy | Wholesale & retail | 1911 |
| Macua Tours Oy | Administrative & support | 2026 |
| MadLink Oy | Transport & logistics | 2024 |
| Made by Aalto Oy | Professional & scientific | 2026 |
| Madeinzoo Oy | Professional & scientific | 2018 |
| Madi Shop Oy | Wholesale & retail | 2025 |
| Mages Oy | Hospitality | 2002 |
| MagiCare Oy | Professional & scientific | 2023 |
| Magiz Oy | Health & social care | 2021 |
| Magnet Invest Oy | Wholesale & retail | 1989 |
| Magnifier Oy | Professional & scientific | 2009 |
| Magnolia Solutions Oy | Professional & scientific | 2009 |
| Magnum Medical Finland Oy | Wholesale & retail | 2004 |
| Magnus Finnish Hold Co Oy | Financial services | 2021 |
| Magpal Oy | Wholesale & retail | 2008 |
| MahaRudra oy | Hospitality | 2019 |
| Mahamantra Oy | Hospitality | 2026 |
| Maharshi Oy | Hospitality | 2022 |
| Mahashakti OY | Financial services | 2017 |
| Mahee Oy | Wholesale & retail | 2025 |
| Mahis Trattoria oy | Hospitality | 2023 |
| Mahku Kiinteistöt Oy | Real estate | 2007 |
| Mahonia Avoin yhtiö | Construction | 2023 |
| Mahti Viihde Oy | Arts & recreation | 2026 |
| Mahtuva Ventures Oy | Hospitality | 2026 |
| Mai Group Oy | Professional & scientific | 2020 |
| MaiVo Beauty Oy | Other services | 2024 |
| Maikoski Kiinteistöt Oy | Real estate | 2010 |
| Mailco Oy | Transport & logistics | 1998 |
| Maillefer Extrusion Oy | Manufacturing | 2001 |
| Maillefer International Oy | Professional & scientific | 2005 |
| Maimed Oy | Administrative & support | 2017 |
| Main Kauneussalonki Oy | Other services | 2017 |
| MainRak Oy | Construction | 2022 |
| Mainegaas Oy | Wholesale & retail | 2023 |
| Mainen Oy | Wholesale & retail | 2021 |
| Mainfix Oy | Information & communication | 1996 |
| Mainio Suomi Oy | Professional & scientific | 2016 |
| Mainos Matti Pulkkinen Oy | Professional & scientific | 1989 |
| Mainos ja Siivouspalvelut Törrönen Oy | Professional & scientific | 2007 |
| Mainos-TeeT Oy | Professional & scientific | 2006 |
| Mainosklassikko Oy | Professional & scientific | 1990 |
| Mainosmaailma Oy | Professional & scientific | 2024 |
| Mainospaino Tampot Oy | Manufacturing | 1992 |
| Mainospalvelu Harry Andersson Oy | Professional & scientific | 1993 |
| Mainospuoti Jari Mäntynen Oy | Professional & scientific | 1996 |
| Mainostoimisto Esplanadi Oy | Professional & scientific | 1997 |
| Mainostoimisto Kallio Oy | Professional & scientific | 1999 |
| Mainostoimisto Kartano Oy | Professional & scientific | 2024 |
| Mainostoimisto Kataja Oy | Professional & scientific | 2022 |
| Mainostoimisto Kaveri Oy | Professional & scientific | 2009 |
| Mainostoimisto Lehtonen, Lindström, Tuomisto Oy | Professional & scientific | 1991 |
| Mainostoimisto Loud Oy | Professional & scientific | 2017 |
| Mainostoimisto Savart Oy | Professional & scientific | 1980 |
| Mainostoimisto Smartgate Oy | Professional & scientific | 2009 |
| Mainostoimisto Stable Oy | Professional & scientific | 1995 |
| Mainostoimisto Työmies Oy | Professional & scientific | 1999 |
| Mainpin Oy | Wholesale & retail | 2024 |
| Maiqqi Oy | Information & communication | 2019 |
| Mairem Oy | Construction | 2018 |
| Mairent Oy | Administrative & support | 2020 |