| Kivikuitu Oy | Information & communication | 2018 |
| Kivirannan Kartano Oy | Hospitality | 1984 |
| Kokkolan Teräslevypalvelu Oy | Administrative & support | 1994 |
| Kokooja Oy | Real estate | 2025 |
| Kone-Tapsa Oy | Wholesale & retail | 1987 |
| Konehuolto Kaitanen Oy | Manufacturing | 2009 |
| Koneistuspalvelu Nieminen Oy | Manufacturing | 1993 |
| Konepaja Survonen Oy | Manufacturing | 2008 |
| Konepalvelu Rehakka Ky | Construction | 2012 |
| Konetekniikka Vainio & Laineenoja | Manufacturing | 1996 |
| Koneurakointi J. Hahko Oy | Mining & quarrying | 2021 |
| Konsula Oy | Information & communication | 1987 |
| Kotiinpäin Huittinen Oy | Agriculture & fishing | 2022 |
| Kotikatu Jokilaakso Oy | Administrative & support | 2020 |
| Kotipalvelu Ilona Oy | Health & social care | 2026 |
| Kuiko Ky | Wholesale & retail | 2005 |
| Kuljetus Hannu O.Kemppainen Oy | Transport & logistics | 2001 |
| Kuljetus L & P Alho Ky | Transport & logistics | 1997 |
| Kuljetus Pasi Koskinen Oy | Transport & logistics | 2017 |
| Kuljetus Samu ja Pasi Alho Oy | Transport & logistics | 2019 |
| Kuljetus V. Mäkelä Oy | Transport & logistics | 2021 |
| Kuljetusliike Ano Heikkilä Oy | Transport & logistics | 1987 |
| Kuljetusliike O. Haavisto Oy | Transport & logistics | 1982 |
| Kuljetusliike T. ja A. Rantanen Oy | Transport & logistics | 1983 |
| Kuljetusliike Tauno Mäkelä Ky | Transport & logistics | 1986 |
| Kuorma-autokorjaamo Mäkelä Oy | Other services | 2025 |
| Kuretekniikka Oy | Construction | 1989 |
| Kurunkoski Invest Oy | Wholesale & retail | 1991 |
| Kuvapassi Oy | Professional & scientific | 2016 |
| Kvr Finland Oy | Construction | 2017 |
| KyheTo Oy | Wholesale & retail | 2025 |
| L-K Partners Oy | Construction | 2023 |
| Lcsa System OY | Information & communication | 2022 |
| LVI- ja Rakennuspalvelu Ojala Ky | Construction | 2008 |
| Laakson Laituriasennus Oy | Construction | 2025 |
| Lakiasiaintoimisto Teerikoski Oy | Professional & scientific | 2002 |
| Lakiasiat Isotalo Oy | Professional & scientific | 1996 |
| Lama-Center Oy | Wholesale & retail | 2009 |
| Latama Ky | Wholesale & retail | 1980 |
| Latelevi Oy | Real estate | 1999 |
| Lauhan Kanoottivuokraamo Oy | Arts & recreation | 2020 |
| Laukku-Mäkelä Oy | Manufacturing | 1990 |
| Laukkutuote Kylväjä Ky | Manufacturing | 1991 |
| Laukkutuote Paunu Ky | Manufacturing | 1989 |
| Laulava Karhu Oy | Hospitality | 2025 |
| Lauri Lähteenmäki Oy | Transport & logistics | 2022 |
| Lautta Consulting Oy | Administrative & support | 2023 |
| Lautta-Data Heikki Kortemäki Ky | Wholesale & retail | 1986 |
| Lautta-Kaluste Koy | Wholesale & retail | 1976 |
| Lautta-Market Oy | Wholesale & retail | 1979 |
| Lauttakylän Betoni Oy | Manufacturing | 1967 |
| Lauttakylän Kuljetus Oy | Transport & logistics | 1990 |
| Lauttakylän Muovi Ky | Manufacturing | 1975 |
| Lauttakylän Putkityö Brunnila Oy | Construction | 1957 |
| Lauttakylän lukion oppilaitososuuskunta | Arts & recreation | 2023 |
| Lauttakylän ravintola oy | Hospitality | 2024 |
| Leafhill Oy | Financial services | 2015 |
| Leafhill Solutions Oy | Administrative & support | 2011 |
| Liikuntakeskus Spiraali Oy | Arts & recreation | 2011 |
| Logs Here Oy | Transport & logistics | 2004 |
| Loimijokivarren jätevesiosuuskunta | Water & waste | 2017 |
| Lola Group Oy | Hospitality | 1998 |
| Lähdehovi Kone Oy | Wholesale & retail | 2012 |
| Lähdehovi Oy | Construction | 2011 |
| Lännen Kiinteistöympyrä Oy | Administrative & support | 2008 |
| Lännen Tilitoimisto Oy | Professional & scientific | 1968 |
| Länsi-Suomen Huoltopalvelu Oy | Manufacturing | 2019 |
| Länsi-Suomen Kiinteistöhuolto Oy | Administrative & support | 2023 |
| Länsi-Suomen Separointi Oy | Agriculture & fishing | 2013 |
| M & H Peippo Oy | Mining & quarrying | 2020 |
| M. Ojapelto Oy | Wholesale & retail | 2008 |
| MAN-Electric Oy | Manufacturing | 2020 |
| MD Electric Oy | Construction | 2023 |
| MHR Holding Oy | Construction | 2020 |
| MR-Asennus Oy | Construction | 2021 |
| MYH Horses Oy | Arts & recreation | 2004 |
| MZ Works Oy | Manufacturing | 2022 |
| Maanrakennus Kariniemi Ky | Construction | 1981 |
| Maanrakennus Lampinen Oy | Construction | 1983 |
| Maaret Aro Ky | Wholesale & retail | 1991 |
| Mabok Oy | Agriculture & fishing | 1994 |
| Mainio Kauppa Oy | Wholesale & retail | 2014 |
| Maintwell oy | Manufacturing | 2024 |
| Maisemarakennus Lahti Oy | Professional & scientific | 2024 |
| Markkinointiapu IdeaTasku Ky | Professional & scientific | 2013 |
| Marko Pohjolainen Oy | Agriculture & fishing | 2013 |
| Marszal Service Oy | Manufacturing | 2025 |
| Matkun Kuljetus Ky | Transport & logistics | 2010 |
| Matmarine Service Group Oy | Manufacturing | 2024 |
| Medilion Oy | Financial services | 2024 |
| Mediset Oy | Construction | 2017 |
| Merstolan Mattopesula ja -kutomo Ky | Other services | 1998 |
| Metalli ja Lvi Lundgren Oy | Construction | 1973 |
| Metallipalvelu Kotiranta Oy | Manufacturing | 2019 |
| Metallityö Laine Oy | Manufacturing | 1988 |
| Metsä KTK Oy | Agriculture & fishing | 2008 |
| Mikko Hurri Oy | Agriculture & fishing | 2011 |
| Milomatic Oy | Wholesale & retail | 2004 |
| Multipirtti Oy | Real estate | 1989 |
| Muovi ja Nahka Kari Ojala Kommandiittiyhtiö | Manufacturing | 2004 |