| Kutomon Kopio Oy | Administrative & support | 2014 |
| Kuuman Asennuspalvelu Oy | Manufacturing | 2024 |
| KuusPlussa Oy | Real estate | 1994 |
| Kuvaamo-Kehystämö Thomsson Oy | Professional & scientific | 1986 |
| Kylmävisio Oy | Professional & scientific | 2024 |
| Kyläfarmari, avoin yhtiö | Financial services | 1996 |
| Kymenlaakson Silmäasemat Oy | Wholesale & retail | 1987 |
| LAZMO Ky | Construction | 2014 |
| LKV Omassa Kotona Oy | Real estate | 2014 |
| LN Events Oy | Arts & recreation | 2025 |
| LO Group Oy | Professional & scientific | 2002 |
| LO Kiinteistöt Oy | Real estate | 2007 |
| LO Rakenne Oy | Construction | 2011 |
| LOG1 Oy | Transport & logistics | 2007 |
| LUXCOSMETICS Ky | Other services | 2014 |
| LVI-Sjöberg oy | Construction | 2024 |
| Laaksosen Laaturengas Oy | Construction | 2000 |
| Laatu-JJ Rakennus Oy | Construction | 2010 |
| Laaturakennus A&I Oy | Construction | 2025 |
| Landemuija Oy | Wholesale & retail | 2023 |
| LapsiperhePalvelu Stark Oy | Health & social care | 2010 |
| Laskenta-10 Oy | Professional & scientific | 2003 |
| Laskentapiste Balanssi Oy | Professional & scientific | 1998 |
| Laskentaplussa Oy | Professional & scientific | 2021 |
| Laurilan Taksit Oy | Transport & logistics | 2021 |
| Leena Kristiina Oy | Health & social care | 2023 |
| Lehtokannas Oy | Transport & logistics | 2020 |
| Lehtovirta & Co Oy | Wholesale & retail | 1992 |
| LeikkiSet Oy | Manufacturing | 2011 |
| Leluliike Hjerp Ky | Wholesale & retail | 1982 |
| Lemmikkieläinliike Vastakarvaan Oy | Wholesale & retail | 2017 |
| Lempi Foods Oy | Wholesale & retail | 2019 |
| Levatrade Oy | Professional & scientific | 1994 |
| Liesjärven Koivula Kiinteistöt Oy | Real estate | 1990 |
| Liha ja Säilyke Oy | Manufacturing | 2002 |
| Lihakilta Oy | Wholesale & retail | 2025 |
| Liikenne Rajala Oy | Transport & logistics | 1996 |
| Lindroos Racing Oy | Arts & recreation | 2010 |
| Linjaliikenne Kivistö Oy | Transport & logistics | 1978 |
| Lintukorpi Invest Oy | Real estate | 1988 |
| Lintukorpi Oy | Construction | 2009 |
| Living Door Oy | Real estate | 2020 |
| Living House Oy | Other services | 2006 |
| Loimi Kierto Oy | Water & waste | 1996 |
| Loimi-Hämeen Jätehuolto Oy | Water & waste | 1995 |
| Loimijoen Kuntapalvelut Oy | Administrative & support | 2009 |
| Loimijoen Tilitoimistopalvelut Oy | Professional & scientific | 2024 |
| Loimijoki Capital Oy | Financial services | 2026 |
| Louhelo-Kiinteistöt Oy | Construction | 1971 |
| Louhinta Tuomola Oy | Construction | 1990 |
| Lähde Hyvään Oloon Oy | Other services | 2015 |
| Lämmin Hoiva Oy | Health & social care | 2022 |
| Lääkäripalvelut Hyvä Sydän Oy | Health & social care | 2012 |
| M & H LVI-suunnittelu avoin yhtiö | Professional & scientific | 2004 |
| M&M EgorSteel Oy | Manufacturing | 2023 |
| M. Aaltonen Ky | Transport & logistics | 2006 |
| M.A. Ravipalvelu Oy | Agriculture & fishing | 2009 |
| M.O.Virtanen Oy | Wholesale & retail | 2008 |
| MAK Media Oy | Professional & scientific | 2018 |
| Metel OY | Construction | 2023 |
| Metsäkuljetus Ylitalo Ky | Agriculture & fishing | 2001 |
| MH Koivisto Oy | Other services | 2001 |
| MHS Invest Oy | Professional & scientific | 2020 |
| MHS Real Estate Oy | Real estate | 2025 |
| MJ Flow Works Oy | Administrative & support | 2026 |
| MR-Talotekniikka Oy | Professional & scientific | 2010 |
| MSN group Oy | Construction | 2026 |
| Ma-Te Group Oy | Construction | 2012 |
| Maanrakennus Salejärvi Oy | Construction | 2023 |
| Maansiirtoliike Matti Knaapi Oy | Construction | 1991 |
| Maatila Känkänen Oy | Agriculture & fishing | 2020 |
| Mai Print Oy | Manufacturing | 1989 |
| Mainos-Kujanpää Ky seur. | Professional & scientific | 2007 |
| Mainossatama Oy | Professional & scientific | 2003 |
| Mainostoimisto Muu Oy | Professional & scientific | 2022 |
| Mainostoimisto Synergia Oy | Professional & scientific | 1999 |
| Majava Bros Oy | Construction | 1989 |
| Makecake Oy | Wholesale & retail | 1997 |
| Mardea avoin yhtiö | Real estate | 2002 |
| Markkinointi- ja mainospalvelu Halminen Ky | Professional & scientific | 2000 |
| Markku Kemppi Kommandiittiyhtiö | Transport & logistics | 1976 |
| Marla Oy | Other services | 2007 |
| Marmola Oy | Financial services | 1997 |
| Match-Makers Ville Koivisto Oy | Information & communication | 1995 |
| Matimek Oy | Manufacturing | 2015 |
| Matkun Atpen Oy | Real estate | 1996 |
| Matti Riitamaa Metsä Oy | Agriculture & fishing | 2000 |
| Maustemajakka Oy | Hospitality | 2020 |
| MediChain Oy | Wholesale & retail | 2009 |
| Medibuild Oy | Health & social care | 2021 |
| MerkintäGroup Oy | Manufacturing | 2020 |
| Merkintäkiinteistöt Ky | Real estate | 2006 |
| Merkintätalo Oy | Professional & scientific | 1997 |
| Mertanen Invest Oy | Professional & scientific | 2023 |
| Metallipaja M. Koskinen Ky | Manufacturing | 1987 |
| MetsäVahos Oy | Transport & logistics | 1982 |
| MiSoft Oy | Professional & scientific | 2005 |
| Miccotrade Ltd Oy | Professional & scientific | 1996 |
| Mikline Oy | Transport & logistics | 1993 |
| Mikon Kaari Oy | Real estate | 1984 |