| Kuljetus Markku Hämäläinen Ky | Transport & logistics | 1998 |
| Kuljetus Mynttinen Oy | Transport & logistics | 2022 |
| Kuljetus Tuuri Oy | Transport & logistics | 1987 |
| Kuljetus V. Ahonen Oy | Transport & logistics | 1971 |
| Kuljetusliike A. Kähkönen Oy | Transport & logistics | 2002 |
| Kuljetusliike Juha Korpivaara Oy | Transport & logistics | 2002 |
| Kullasvaara Oy | Transport & logistics | 2021 |
| Kulmatontti Oy | Real estate | 2009 |
| Kulta- ja Hopeapaja Korundi Oy | Manufacturing | 2014 |
| Kultataide Jewelry Castings Oy | Manufacturing | 2016 |
| Kuntohuone Oy | Arts & recreation | 2014 |
| Kuntokeskus Ykkönen Ky | Arts & recreation | 1994 |
| Kuopion DK-konsult Oy | Professional & scientific | 1986 |
| Kurjenniemen vesihuolto-osuuskunta | Water & waste | 2001 |
| Kursio Oy | Education | 2026 |
| Kuusaan Auto ja Lasi Oy | Other services | 2018 |
| Kuusaan KK Härkönen Oy | Other services | 1988 |
| Kuusaan LiiviShop Oy | Wholesale & retail | 2010 |
| Kvl Rakennusapu Oy | Construction | 2021 |
| Kvl Rengasteam Oy | Wholesale & retail | 2003 |
| Kylmähuolto Kalsea Oy | Construction | 2012 |
| Kylmähuolto Resek Oy | Construction | 1990 |
| KymRec Oy | Manufacturing | 2026 |
| Kymen AOV-Huollot Oy | Other services | 1990 |
| Kymen AP Oy | Wholesale & retail | 2023 |
| Kymen ATH-Myynti Oy | Financial services | 1989 |
| Kymen Asfaltti Oy | Construction | 2008 |
| Kymen Betonileikkaus Ky | Construction | 1985 |
| Kymen Charterline Oy | Transport & logistics | 1996 |
| Kymen Electric Oy | Construction | 1993 |
| Kymen Habita Oy | Real estate | 2004 |
| Kymen Hautauspalvelu Kovanen Kommandiittiyhtiö | Other services | 1973 |
| Kymen Hormihuolto Oy | Administrative & support | 2005 |
| Kymen Ilma Ky | Construction | 1992 |
| Kymen Kattokeskus Group Oy | Professional & scientific | 2022 |
| Kymen Kielipalvelu Oy | Professional & scientific | 1986 |
| Kymen Kiinteistötoimisto Oy LKV | Real estate | 2019 |
| Kymen Kylmärinki Oy | Construction | 1991 |
| Kymen Leipomo Oy | Wholesale & retail | 2020 |
| Kymen Mediapaja Oy | Arts & recreation | 2020 |
| Kymen Osarak Oy | Professional & scientific | 1991 |
| Kymen Parketti Oy | Construction | 1995 |
| Kymen Porakopale Oy | Wholesale & retail | 1993 |
| Kymen Rakennesukellus Oy | Construction | 2024 |
| Kymen STG Oy | Construction | 1994 |
| Kymen Seudun Osuuskauppa | Wholesale & retail | 2012 |
| Kymen Sähkötyö Oy | Construction | 2010 |
| Kymen Teollisuuskoneistus Oy | Manufacturing | 1994 |
| Kymen Tilitiimi Oy | Professional & scientific | 1990 |
| Kymen Työturvallisuuspalvelut Ky | Education | 2020 |
| Kymen Varaosahalli Oy | Wholesale & retail | 1988 |
| Kymen Voima-Avain avoin yhtiö | Health & social care | 2014 |
| Kymen lava ja autovaruste Ky | Manufacturing | 1983 |
| Kymenlaakson Hevosklinikka Oy | Professional & scientific | 2008 |
| Kymenlaakson Kampuskiinteistöt Oy | Real estate | 2012 |
| Kymenlaakson Rakennus Oy | Construction | 1968 |
| Kymenlaakson Äänimainonta Oy | Information & communication | 1988 |
| Kymi Riding Oy | Arts & recreation | 2014 |
| Kymi-Karjalan Komediatuotanto Oy | Arts & recreation | 2012 |
| KymiRing Oy | Arts & recreation | 2013 |
| Kymiaudit Ky | Professional & scientific | 2018 |
| Kymimotors Oy | Wholesale & retail | 2016 |
| Kymrea Oy | Wholesale & retail | 2023 |
| Kyynaama Oy | Information & communication | 2021 |
| Kyyti ja Remontti Oy | Transport & logistics | 2026 |
| Kärkipalvelut Ky | Transport & logistics | 2004 |
| Kärkitarvike Oy | Wholesale & retail | 2006 |
| Käsityöliike Linnea Ky | Wholesale & retail | 2005 |
| Käärmekeitto Oy | Hospitality | 2005 |
| L.A. Company Oy | Hospitality | 2015 |
| LAMYKIN'S INTERNATIONAL Oy | Hospitality | 2013 |
| Len Tam OY | Hospitality | 2018 |
| LF Investors Oy | Financial services | 2023 |
| Liibalaaba OY | Hospitality | 2012 |
| LIT Holding Oy | Financial services | 2025 |
| LT-Kiinteistöpalvelut Oy | Construction | 1998 |
| LVI-Kolmikko Oy | Construction | 2014 |
| La Vie De Marrakech Oy | Wholesale & retail | 2014 |
| Laaduntekijä Oy | Administrative & support | 2014 |
| Lakebrook Oy | Financial services | 2021 |
| Lakiasiaintoimisto Lehto & Lehto Oy | Professional & scientific | 1991 |
| Lakitoimisto Carina Oy | Professional & scientific | 1987 |
| Laktek Engineering Oy | Professional & scientific | 2016 |
| Lapinjärven Siivouspalvelu Ky | Administrative & support | 2000 |
| Lapsekas Oy | Wholesale & retail | 1992 |
| Lasinilkka Oy | Financial services | 2023 |
| Lauri Halonen Oy | Arts & recreation | 2026 |
| Laverda Ky | Real estate | 2004 |
| LeadBoost Oy | Professional & scientific | 2026 |
| Lean Stream Oy | Professional & scientific | 2024 |
| Leena Akkanen Ky | Transport & logistics | 1991 |
| Leftlane Oy | Transport & logistics | 2009 |
| Lehmuskulma Oy | Real estate | 2022 |
| Lehtomäen Hiuspiste Ky | Other services | 2005 |
| Leksoni Oy | Construction | 2024 |
| Leon Wood Oy | Wholesale & retail | 1990 |
| LifeNow Oy | Information & communication | 2016 |
| Liljander Yhtiöt Oy | Financial services | 2024 |
| Lining Tec Oy | Professional & scientific | 1989 |
| Linjaliikenne Martti Laurila Oy | Transport & logistics | 1976 |