| Klosterøya Vest Næring AS | Transport & logistics | 2013 |
| Klunken Blessenborg Invest AS | Financial services | 2014 |
| Klyvevegen 99 AS | Construction | 2021 |
| KM Bygg & Anlegg AS | Professional & scientific | 2017 |
| KM Bygg & Anlegg Eiendomsutvikling AS | Real estate | 2018 |
| KM Bygg & Anlegg Invest AS | Professional & scientific | 2017 |
| KM Utearbeider Da | Agriculture & fishing | 2025 |
| KM8 Holding AS | Wholesale & retail | 2023 |
| KMK. Eiendom AS | Real estate | 2022 |
| Knatten Ski AS | Financial services | 2005 |
| Knerten Familiebarnehage Da | Education | 1996 |
| KNG 18 AS | Wholesale & retail | 2023 |
| Knippe AS | Real estate | 2016 |
| Knut Borgersen Holding AS | Real estate | 2005 |
| Knut Fosse AS | Financial services | 2010 |
| Knut Navestad Utleie & Tjenester AS | Construction | 2014 |
| Knutshaug Transport AS | Transport & logistics | 2013 |
| Knøttne Familiebarnehage AS | Education | 2016 |
| Kobber Frisør AS | Other services | 2014 |
| Kogger & Bue AS | Information & communication | 2024 |
| Kokk Sokker Og Sko AS | Real estate | 2016 |
| Kollen Gaustatoppen AS | Real estate | 2012 |
| Kollen Skilodge AS | Real estate | 2021 |
| Kollenvegen 6 AS | Real estate | 2014 |
| Kollenveien 16 AS | Professional & scientific | 2022 |
| Komet Netthandel AS | Wholesale & retail | 2021 |
| Kompetansepartner & Maskinutleie AS | Administrative & support | 2016 |
| Komplett Håndverkstjenester AS | Construction | 2013 |
| Kongens Gate 5B AS | Real estate | 2018 |
| Kongensgate 12 AS | Real estate | 2020 |
| Kongensgate 14 AS | Real estate | 1990 |
| Kongensgate 16 Skien AS | Real estate | 2016 |
| Kongensgate 20A AS | Real estate | 2019 |
| Kongerød Eiendom AS | Real estate | 2013 |
| Kongerødvegen 1 AS | Real estate | 2020 |
| Konosør AS | Hospitality | 2022 |
| Konsulink AS | Administrative & support | 2023 |
| Kontni AS | | 2024 |
| Kontor- Og Prosjektpartner AS | Professional & scientific | 2024 |
| Koordinatorskolen AS | Education | 2015 |
| Korkmaz Holding AS | | 2026 |
| Kosesa AS | | 2018 |
| KPC AS | Other services | 2018 |
| KPS Drift & Personell AS | Administrative & support | 2007 |
| KPS Eiendom AS | Real estate | 2015 |
| KR Fjeld AS | Wholesale & retail | 1981 |
| Kraaka Kapital AS | | 2021 |
| Krabberødveien Boligutvikling AS | Real estate | 2020 |
| Krafs AS | Construction | 2017 |
| Kragerø Brygge AS | Real estate | 1998 |
| Kragerø Og Grenland Økonomiservice AS | Professional & scientific | 2012 |
| Kranringen AS | Transport & logistics | 1989 |
| Kraus Invest AS | | 2019 |
| Kred Gruppen AS | Real estate | 2022 |
| Kremen Av Kremen AS | Hospitality | 2025 |
| Kremen Herkules AS | Hospitality | 2016 |
| Krinkel-Kroken AS | Wholesale & retail | 2012 |
| Kriskvcs AS | Education | 2025 |
| Krist Invest AS | | 2026 |
| Kristiansen Betongpumping AS | Manufacturing | 1995 |
| Kristine Danielsen AS | Wholesale & retail | 2003 |
| Kristoffer Holding AS | Financial services | 2018 |
| Kristoffer Sneltvedt Holding AS | | 2021 |
| Krogsgård Holding AS | | 2020 |
| Krogstads Holding AS | Professional & scientific | 2021 |
| Kroken Naturstein AS | Mining & quarrying | 2017 |
| Krossli AS | Professional & scientific | 2018 |
| Kryptx Holding AS | | 2023 |
| KS Graveservice Ans | Construction | 1989 |
| KSH Transport AS | Transport & logistics | 1986 |
| KSM AS | Manufacturing | 1996 |
| KST Holding AS | Financial services | 2005 |
| Kulturlandskaperne AS | Education | 2013 |
| Kulåsen Vann Og Avløp SA | Water & waste | 2008 |
| Kunstgjødsel AS | Information & communication | 2006 |
| Kurt a. Anderson AS | Construction | 2022 |
| Kushar Transport AS | Transport & logistics | 2022 |
| Kvalitet Bilpleie AS | Other services | 2016 |
| Kvalsvik AS | Wholesale & retail | 2020 |
| Kvam Transport AS | Transport & logistics | 2020 |
| Kvendboe AS | Real estate | 2011 |
| Kverndalen Fot & Velvære AS | Health & social care | 2025 |
| Kverndalsgata 8 AS | Real estate | 2021 |
| Kverndalsgt. 1 AS | Real estate | 2008 |
| Kvernodden Terrasse Utbygging AS | Real estate | 2020 |
| KVM Eiendom AS | Real estate | 2023 |
| KWS Eiendom AS | Real estate | 2008 |
| L&T Eiendom AS | Real estate | 2015 |
| L.T.B. Holding AS | Real estate | 2005 |
| L/K Holding AS | | 2024 |
| La Beauty AS | Other services | 2017 |
| La Bodega Skien AS | Hospitality | 2021 |
| Lagopus Holding AS | Real estate | 2008 |
| Lajordet Bjønnes Vann & Avløp SA | Water & waste | 2010 |
| Lakkspesialisten Skien AS | Wholesale & retail | 2022 |
| Lal Holding AS | | 2005 |
| Lal Holding II AS | | 2026 |
| Landmannsgården AS | Real estate | 2001 |
| Landskapsentreprenøren AS | Administrative & support | 2018 |
| Landstadsgate 41 SA | Real estate | 1950 |