| Kjølnes Ring 2 AS | Real estate | 2008 |
| Kjølnesjordet Utvikling AS | Real estate | 2023 |
| Kjørbekk Næringspark AS | Real estate | 2007 |
| Kjørbekkdalen 12 D AS | Real estate | 2007 |
| Kjøretøydata SA | Information & communication | 2020 |
| Kjøretøyopplysninger Da | Information & communication | 2022 |
| KKF Eiendom AS | Real estate | 2016 |
| Klara Telemark AS | Wholesale & retail | 2014 |
| Klebetekst AS | Manufacturing | 1990 |
| Kleppe Holding AS | Real estate | 2021 |
| KLG Cosmetics Limited Nuf | Wholesale & retail | 2010 |
| Klikk Holding AS | Wholesale & retail | 2021 |
| Klikkmentor Da | Professional & scientific | 2022 |
| Klille AS | | 2024 |
| Klosterøya Næringspark AS | Real estate | 2007 |
| Klosterøya Vest Tomter AS | Real estate | 2025 |
| Klqd AS | Information & communication | 2016 |
| KLUB7 AS | Professional & scientific | 2023 |
| KMH Eiendom AS | Real estate | 2007 |
| KMH Elektro AS | Professional & scientific | 2006 |
| Knardalstrand Engineering AS | Professional & scientific | 2016 |
| Knudsen Consulting AS | Professional & scientific | 2025 |
| Knutepunkt Porsgrunn AS | Real estate | 2011 |
| Knutsen Og Halvorsen Invest AS | Real estate | 2020 |
| Kokkers AS | Financial services | 2005 |
| Kokkersvold Eiendom AS | Real estate | 2007 |
| Kokleheia Eiendom AS | | 2018 |
| Kokleheia Invest AS | Real estate | 2021 |
| Koks Brasserie AS | Hospitality | 2009 |
| Kompani Olsen AS | Real estate | 2016 |
| Kompis Eiendom AS | Real estate | 2018 |
| Kongerød Bolig AS | Real estate | 2022 |
| Kongmo AS | Wholesale & retail | 2022 |
| Kongsgård Invest AS | Financial services | 2015 |
| Koniro AS | Arts & recreation | 2015 |
| Konsept Bolig AS | Construction | 2022 |
| Kontorpartner AS | Wholesale & retail | 2010 |
| Kontram AS | Wholesale & retail | 2002 |
| Kopite Invest AS | | 2021 |
| Korde Advokat AS | Professional & scientific | 2025 |
| Korde Holding AS | Real estate | 1987 |
| Korten Eiendom AS | Real estate | 2000 |
| Kraemer AS | Wholesale & retail | 1998 |
| Krane Kobber Og Blikk Nuf | Construction | 2017 |
| Kreativ Familiebistand AS | Health & social care | 2012 |
| Kreativ IT AS | Information & communication | 2012 |
| Kristine Danielsen Hovenga AS | Wholesale & retail | 2010 |
| Kristoffersen Og Kristoffersen AS | Real estate | 2025 |
| Krogstad Foto AS | Professional & scientific | 2025 |
| Krydderverket AS | Wholesale & retail | 2025 |
| Kråkeslottet Eiendom AS | Real estate | 2002 |
| Kuciak Solutions AS | Professional & scientific | 2025 |
| Kulltangen Regnskap AS | Professional & scientific | 2010 |
| Kulltangvegen 5 AS | Real estate | 2001 |
| Kultursone AS | Health & social care | 2014 |
| Kursholder Hunnestad AS | Education | 2024 |
| Kvam Flytting & Transport AS | Transport & logistics | 2025 |
| Kvast Invest AS | | 2026 |
| Kvelland Holding AS | | 2015 |
| Kvina Energy AS | Manufacturing | 2021 |
| Kvist Og Kvast Anleggsgartner AS | Administrative & support | 2005 |
| Kåg Invest AS | | 2020 |
| L Grønaasen Transport AS | Transport & logistics | 1989 |
| L-K Invest AS | Financial services | 2014 |
| L4 Holding AS | | 2020 |
| La Femme AS | Other services | 2005 |
| La-Invest AS | Professional & scientific | 2021 |
| Laagasken AS | | 2019 |
| LAGER1 AS | Real estate | 2017 |
| Lagerblad Holding AS | | 2025 |
| Lagertorget AS | Information & communication | 2026 |
| Lagra AS | Real estate | 2025 |
| Lajordet Hytteeieres Parkeringslag SA | Real estate | 2017 |
| Lam AS | Health & social care | 2022 |
| Langangsfjorden Vest Va-Drift SA | Water & waste | 2015 |
| Langesund Utvikling AS | Real estate | 2022 |
| Langlim Transporttjenester AS | Transport & logistics | 2015 |
| Langman Holding AS | | 2025 |
| Langmyra 11 AS | Real estate | 2018 |
| Langmyra 2 AS | Real estate | 2018 |
| Langmyra 6 AS | Real estate | 2007 |
| Langmyra Holding AS | Real estate | 2020 |
| Langmyrvegen 30 AS | Real estate | 1989 |
| Larsen Bilservice AS | Other services | 2020 |
| Lascala Consulting AS | Real estate | 2005 |
| Last Dance Holding AS | | 2026 |
| Laugstol AS | Construction | 1992 |
| Lauritz Skjenkestue Porsgrunn Da | Hospitality | 2003 |
| Lawsuit Property AS | Real estate | 2017 |
| Layan Frisør AS | Other services | 2022 |
| Layerone AS | Professional & scientific | 2021 |
| Lead Mill AS | Professional & scientific | 2025 |
| Leasepro AS | Administrative & support | 2021 |
| Lede AS | Energy | 1997 |
| Lege Arve Rennesund AS | Health & social care | 2009 |
| Lege Catharina Hovland Sannes AS | Health & social care | 2014 |
| Lege Øystein Line AS | Health & social care | 1990 |
| Leidarstein AS | | 2013 |
| Leirgata Utvikling AS | Real estate | 2023 |
| Leirvollen 1 AS | Real estate | 1984 |