| MSD scaffolding Oy | Construction | 2022 |
| MSK Rakennus Oy | Construction | 2020 |
| MSL Group Oy | Construction | 2021 |
| MT Rent Fi OY | Construction | 2020 |
| MTC Construction Oy | Construction | 2023 |
| Mukavasti OY | Hospitality | 2021 |
| MVR Matikainen Oy | Transport & logistics | 2009 |
| MX Sushi OY | Hospitality | 2020 |
| MXK Entertainment Finland Oy Ltd. | Professional & scientific | 2006 |
| MaKaplan Oy | Hospitality | 2021 |
| MaKo Publishing Oy | Wholesale & retail | 2024 |
| Maailmanpesu oy | Other services | 2023 |
| Maal.fi Oy | Wholesale & retail | 2023 |
| Maalikauppa V&O Oy | Wholesale & retail | 2012 |
| Maanrakennus Korvenkaivu Oy | Real estate | 2013 |
| Maanrakennus Pirilä Oy | Construction | 1989 |
| Maanrakentajapaikalle Oy | Construction | 2022 |
| Macostad Oy | Professional & scientific | 2023 |
| Macring Service Oy | Manufacturing | 2010 |
| Madame Fere Oy | Wholesale & retail | 2021 |
| Madoira Oy | Manufacturing | 2015 |
| Magic Games Oy | Education | 1999 |
| Maihe Oy | Wholesale & retail | 2020 |
| Maija Strandberg Oy | Wholesale & retail | 2020 |
| Mail Factory Oy | Transport & logistics | 1987 |
| Mainonnan Vuolas Vastavirta Oy | Professional & scientific | 2009 |
| Maison Miska Kettu Oy | Wholesale & retail | 2023 |
| Majakka Watersports Oy | Administrative & support | 2020 |
| Majavan tila osk | Real estate | 2024 |
| Major Sales Oy | Professional & scientific | 2020 |
| Mak-Kone Oy | Manufacturing | 2009 |
| Make On Stage Productions Ky | Professional & scientific | 2006 |
| Makea Talot Oy | Construction | 2022 |
| Makeeagency Oy | Wholesale & retail | 2016 |
| Makkis ja Pekkis 2 oy | Hospitality | 2020 |
| Makkis ja Pekkis Oy | Hospitality | 2019 |
| Mako Enterprises Oy | Information & communication | 2022 |
| Maksamatta Oy | Administrative & support | 2020 |
| Maksusitoumuspalvelu BD Oy | Financial services | 2022 |
| Maku Finland Oy | Hospitality | 2015 |
| Maku Suomi Oy | Hospitality | 2017 |
| Mala Hala Oy | Transport & logistics | 2010 |
| Malisilla Oy | Administrative & support | 1994 |
| Malmin herkku Oy | Hospitality | 2018 |
| Mamba time Oy | Other services | 2021 |
| Man - Grove ASSETS & FINANCE Oy | Financial services | 2022 |
| Management Bureau Falcken Oy Ab | Professional & scientific | 2006 |
| Mandura Oy | Construction | 2023 |
| Maneki Matcha house Oy | Hospitality | 2021 |
| Mangiafuoco Oy | Other services | 2025 |
| Mania Service Oy | Transport & logistics | 2020 |
| Mankkaan Taksihuolto Oy | Transport & logistics | 2008 |
| Manna Invest Ab | Financial services | 1988 |
| Mar Kuj Oy | Manufacturing | 2021 |
| MarMex Rakennus Oy | Construction | 2019 |
| MarSal Invest Oy | Financial services | 2019 |
| Marek Trading Oy | Construction | 2020 |
| Marin Sport Oy | Wholesale & retail | 1989 |
| Marioneiti Oy | Other services | 2020 |
| Marita Taavitsainen Company Oy | Other services | 2020 |
| Marjolia Oy | Professional & scientific | 2022 |
| Marjomäen Kiinteistö Oy | Wholesale & retail | 2014 |
| Marjoniemi Oy | Construction | 1990 |
| Marketing SAV Oy | Professional & scientific | 2024 |
| Markkinakeskus Karjula-Consult Oy | Professional & scientific | 1996 |
| Markkinointi Miska Oy | Construction | 1990 |
| Markkinointi Tareteam Oy | Wholesale & retail | 1995 |
| Marko E Salonen Oy | Construction | 2019 |
| Marmeko Oy | Construction | 2017 |
| Marpartner Oy | Construction | 2012 |
| Marsalis Rakennus Oy | Construction | 2009 |
| Marshal Bamse Oy | Transport & logistics | 2023 |
| Marteva Oy | Construction | 2019 |
| Martin Works Oy | Construction | 2023 |
| Martti Kansanen O.Y. | Wholesale & retail | 1941 |
| Marttila Export Oy | Wholesale & retail | 2022 |
| Marven Finland Oy | Construction | 2021 |
| Marwet rakennus Oy | Construction | 2017 |
| Masal Oy | Hospitality | 2005 |
| Maskia Oy | Wholesale & retail | 2020 |
| Massage Finland Oy | Health & social care | 2019 |
| Mast- och tornunderhåll Sverige Aktiebolag filial i Finland | Construction | 2022 |
| Master Dressage Oy | Arts & recreation | 2007 |
| Mastercom Oy | Information & communication | 2003 |
| Masterpinnoitus Oy | Construction | 2019 |
| MatKe Oy | Administrative & support | 2018 |
| Matchfinn Oy | Professional & scientific | 2011 |
| Matto Autio Ky | Manufacturing | 1979 |
| MaxAuto korjaamo & maalaamo Oy | Other services | 2017 |
| MaxFit Oy | Other services | 2020 |
| MaxMax palvelut Oy | Construction | 2019 |
| Maxtom Oy | Professional & scientific | 2014 |
| McElä Oy | Professional & scientific | 2021 |
| McToy Ky | Wholesale & retail | 1993 |
| MeBoon AB | Hospitality | 2023 |
| MeTaPe OY | Construction | 2022 |
| Meat Gangsters Oy | Hospitality | 2020 |
| Med Oasis Ab Oy | Health & social care | 2023 |
| MedScope Oy | Health & social care | 2006 |
| MediKiru Oy | Health & social care | 2025 |