| Maripro Oy | Professional & scientific | 2013 |
| Maris Treehouse Kämp Oy | Hospitality | 2024 |
| Marisampo Oy | Professional & scientific | 2009 |
| Maritimus Trading Oy | Professional & scientific | 2023 |
| Mariundo Oy | Financial services | 2018 |
| Marius Telineet Oy | Administrative & support | 2022 |
| Marja Bar Oy | Hospitality | 2026 |
| Marja Entrich Oy | Wholesale & retail | 1999 |
| Marja Kurki Oy | Wholesale & retail | 1992 |
| Marja Palmujoki Ky | Professional & scientific | 1985 |
| Marjakuusi Oy | Real estate | 2024 |
| Marjalinna Oy | Health & social care | 1995 |
| Marjapirtti Oy | Financial services | 1965 |
| Marjasuolaine Holding Oy | Financial services | 2021 |
| Marjatri Oy | Health & social care | 2018 |
| Marjatta & Kaisa Oy | Professional & scientific | 2016 |
| Marjatta Erkkilä oy | Health & social care | 2024 |
| Marjo Music Oy | Arts & recreation | 2026 |
| Marjon Holding Oy | Financial services | 2023 |
| Marjut Louhula Oy | Professional & scientific | 1995 |
| Mark & Co Oy | Construction | 2016 |
| Mark IV Oy | Information & communication | 2024 |
| Mark Kustannus Oy | Education | 1984 |
| Mark Mindubaev Oy | Professional & scientific | 2024 |
| Mark Richard's Business English Oy | Education | 1998 |
| Mark Vegas Oy | Professional & scientific | 2014 |
| Mark&Value Oy | Professional & scientific | 1978 |
| Markaid Oy | Professional & scientific | 1991 |
| Markan Sähkö Oy | Construction | 2022 |
| Markasta Oy | Professional & scientific | 2026 |
| Markenas Oy | Professional & scientific | 2015 |
| Market Pay Finland Oy | Financial services | 2026 |
| MarketReached Technologies Oy | Information & communication | 2018 |
| Marketing (&) Mischief Finland Oy Ltd | Professional & scientific | 2010 |
| Marketing Agency Volpe Oy | Professional & scientific | 2022 |
| Marketing Marina Oy | Professional & scientific | 2023 |
| Marketing Marina Services Oy | Professional & scientific | 2021 |
| Marketing Mentor Finland Oy | Professional & scientific | 2024 |
| Marketing by Ida Oy | Professional & scientific | 2023 |
| Marketingwave Oy | Professional & scientific | 2021 |
| Marketrav Oy | Financial services | 1987 |
| Marketta Airasmaa Oy | Wholesale & retail | 2006 |
| Markit Finland IT Procurement Oy | Information & communication | 1997 |
| Markit Oy | Professional & scientific | 1993 |
| Markka Capital Oy | Financial services | 2026 |
| Markka Investment Oy | Professional & scientific | 2020 |
| Markkamasuuni Oy | Other services | 2014 |
| Markkanen Dream Billing Oy Ltd | Arts & recreation | 2020 |
| Markkanen Holding Oy | Financial services | 2024 |
| Markkinakaasu Oy | Energy | 2020 |
| Markkinakonsultti Suomi Oy | Manufacturing | 2018 |
| Markkinoinnin Muurahainen Oy | Professional & scientific | 2016 |
| Markkinointi & Consulting LiiCo Oy | Manufacturing | 1982 |
| Markkinointi & Myynti TH Oy | Professional & scientific | 2013 |
| Markkinointi Ashour Ky | Hospitality | 1994 |
| Markkinointi Bravuuri Oy | Professional & scientific | 2005 |
| Markkinointi Lamberg Oy | Manufacturing | 1990 |
| Markkinointi P. Suhonen Oy | Professional & scientific | 1973 |
| Markkinointi Pakkaset Oy | Wholesale & retail | 1983 |
| Markkinointi Simo Rantanen Oy | Wholesale & retail | 1989 |
| Markkinointi Sumoi Oy | Professional & scientific | 2014 |
| Markkinointi Tihveräinen Oy | Wholesale & retail | 2003 |
| Markkinointi- ja mainostoimisto Pähkinä Oy | Professional & scientific | 1986 |
| Markkinointiosakeyhtiö i2 | Professional & scientific | 2008 |
| Markkinointipalvelu IPF Oy | Wholesale & retail | 2023 |
| Markkinointipalvelu Nyholm Kommandiittiyhtiö | Wholesale & retail | 1978 |
| Markkinointitoimisto Alkuvoima Oy | Professional & scientific | 2006 |
| Markkinointitoimisto Dynamiitti Oy | Professional & scientific | 2017 |
| Markkinointitoimisto FissioMedia Oy | Professional & scientific | 2013 |
| Markkinointitoimisto Johdin Oy | Professional & scientific | 2004 |
| Markkinointitoimisto Jälki360 Oy | Professional & scientific | 2005 |
| Markkinointitoimisto Meena K. Oy | Professional & scientific | 1989 |
| Markkinointitoimisto OZO Oy | Professional & scientific | 1994 |
| Markkinointitoimisto Pinakle Oy | Professional & scientific | 2019 |
| Markkinointitoimisto Struktuuri Oy | Professional & scientific | 2021 |
| Markkinointitoimisto WDS Oy | Professional & scientific | 2010 |
| Markkinointitutkimus Infontain Oy | Professional & scientific | 1993 |
| Markkinointiviestintä Olennainen Oy | Professional & scientific | 2017 |
| Markkinointiviestintä Peltonen Ky | Professional & scientific | 1981 |
| Markkinointiviestintä Sowelu Oy | Professional & scientific | 2018 |
| Markku Helenius Ky | Wholesale & retail | 1983 |
| Markku Hietala RE Oy | Financial services | 2008 |
| Markku Issakainen Oy | Wholesale & retail | 1989 |
| Markku Jämsä Oy | Professional & scientific | 2023 |
| Markku Järventaka Ky | Wholesale & retail | 1999 |
| Markku Kivistö Oy | Financial services | 2025 |
| Markku Mäkelä Music Oy | Manufacturing | 2021 |
| Markku Tilli työnohjaus ja coaching Oy | Professional & scientific | 2021 |
| Markku Tolvi Oy | Professional & scientific | 2020 |
| Markkunointi Oy | Professional & scientific | 2024 |
| Marklex Oy | Professional & scientific | 2000 |
| Marko Jolo Oy | Arts & recreation | 2013 |
| Marko Karppinen & Co. Oy | Information & communication | 2004 |
| Marko Muona Oy | Professional & scientific | 2015 |
| Marko Uusitalo Consulting Oy | Information & communication | 1981 |
| Markon Shampooputiikki Oy | Other services | 2025 |
| Markpa Oy | Construction | 1994 |
| Marksman Finland Oy | Transport & logistics | 2006 |
| Markun Neon Oy | Construction | 2020 |
| Markus Bergman Oy | Professional & scientific | 1997 |