| Jørgens Eiendom AS | Real estate | 2011 |
| K Simonsen Transport AS | Transport & logistics | 2001 |
| K-H.F Eiendom AS | Real estate | 2008 |
| K. Simonsen Holding AS | Transport & logistics | 2011 |
| K. Simonsen Kran AS | Construction | 2021 |
| K. Simonsen Storbilsenter AS | Other services | 2012 |
| K39 Harstad AS | Other services | 2012 |
| Kaarbø Eiendom AS | Real estate | 2017 |
| Kaarbø Kontor AS | Real estate | 2019 |
| Kaarbø Utvikling AS | Real estate | 2018 |
| Kaarbøkvarteret AS | Real estate | 2020 |
| Kada Eiendom AS | Real estate | 2024 |
| Kamil's AS | Wholesale & retail | 2017 |
| Kan Rør AS | Construction | 2016 |
| Kan Rør Holding AS | | 2025 |
| Kane Kasserollesvingeri AS | Hospitality | 2025 |
| Kanebog AS | Real estate | 2021 |
| Kanebog Gruppen AS | Wholesale & retail | 2016 |
| Kanebogen Sko AS | Wholesale & retail | 1996 |
| Kani AS | Professional & scientific | 2020 |
| Kanstrøm AS | Wholesale & retail | 2024 |
| Kari Mettes Trafikkskole AS | Education | 2024 |
| Karlsen Eiendom AS | Real estate | 1984 |
| Kasey Hairstudio AS | Other services | 2018 |
| Kasfjord Båthavn SA | Arts & recreation | 1988 |
| Katarina AS | Professional & scientific | 2024 |
| Katrine Børseth AS | Health & social care | 2019 |
| Katthult Products AS | Manufacturing | 2016 |
| Kaurinart Ans | Wholesale & retail | 2018 |
| Kei Seljestad AS | Real estate | 2021 |
| Kenneth Simonsen Kranpartner AS | Transport & logistics | 2025 |
| KH Harstad AS | Construction | 2020 |
| Kic Invest AS | Financial services | 2005 |
| Kii Holding AS | | 2023 |
| Kikke Invest AS | Financial services | 2005 |
| Kilaaker Gård Da | Agriculture & fishing | 2019 |
| Kilbotn Vannverk SA | Water & waste | 1964 |
| Kilkam Anlegg AS | Real estate | 2009 |
| Killi Eiendom Harstad AS | Real estate | 2013 |
| Kim AS | | 2012 |
| Kinarestaurant AS | Hospitality | 2005 |
| Kiropraktor Helge Haavaag AS | Health & social care | 2017 |
| Kiropraktorklinikken Harstad AS | Health & social care | 2012 |
| Kjaska AS | Real estate | 2021 |
| Kjellin Consulting & Services AS | Professional & scientific | 2022 |
| Kjelseth Rekruttering & Rådgivning AS | Professional & scientific | 2005 |
| Kjempenhøy Eiendom AS | Real estate | 2018 |
| Kjetil Krokeide Holding AS | Real estate | 2015 |
| Kjeveortoped Pettersen AS | Health & social care | 1995 |
| Kjøpesenter Nord AS | Real estate | 2002 |
| Klippsi AS | Other services | 2020 |
| Klokkergården Eiendom AS | Real estate | 2021 |
| Klubbholmen 11 AS | Real estate | 2020 |
| Klubbholmen 4 AS | Real estate | 2001 |
| Klubbholmen 5 AS | Real estate | 2017 |
| Klubbholmen 6 A-B AS | Real estate | 1996 |
| Klubbholmen 6C AS | Real estate | 2010 |
| Klubbholmen 9 AS | Real estate | 2006 |
| Klubbveien 5 AS | Real estate | 1988 |
| Kobbhullet Eiendom AS | Real estate | 2013 |
| Kokkens Mat AS | Wholesale & retail | 1994 |
| Kombitrans & BJT AS | Administrative & support | 2020 |
| Kompis Harstad AS | Hospitality | 2022 |
| Kongshytta AS | Wholesale & retail | 2012 |
| Kongsveien 14 AS | Real estate | 2026 |
| Kongsveien Eiendom Harstad AS | Real estate | 2023 |
| Konsulentpartner Harstad AS | Professional & scientific | 2013 |
| Kontakt Schjelderup Ans | | 1993 |
| Kontor Og Interiør Harstad AS | Wholesale & retail | 2005 |
| Kris Myhre AS | Professional & scientific | 2020 |
| Kristian Holst AS | Real estate | 1981 |
| Kristian Krogstad Holding AS | Health & social care | 2024 |
| Krøtø Holding AS | | 2025 |
| Krøtø-Olsen Holding AS | | 2024 |
| Krøtø-Olsen Transport AS | Transport & logistics | 2014 |
| KTV Group Nordland AS | Professional & scientific | 2024 |
| Kube Invest AS | Real estate | 2006 |
| Kulltomten AS | Real estate | 2017 |
| Kupa AS | Professional & scientific | 2004 |
| Kvannes AS | | 2015 |
| Kvannes Invest AS | | 2018 |
| Kvannes Stikkledningslag | Water & waste | 2013 |
| Kvilstad Holding AS | | 2024 |
| Kvitebjørn Foto AS | Professional & scientific | 2012 |
| Kvitvik Holding AS | Real estate | 2021 |
| Kystlager AS | Real estate | 2025 |
| Kåringen Næringspark AS | Real estate | 2021 |
| L.E Holding AS | | 2024 |
| L.M Holding AS | | 2024 |
| Laboremus AS | Wholesale & retail | 1999 |
| Lafamilia Familieterapi AS | Health & social care | 2024 |
| Lakksenteret Harstad AS | Other services | 2005 |
| Lamo Liv Og Leire AS | Health & social care | 2025 |
| Landslide AS | Administrative & support | 2014 |
| Landsås Idrettspark AS | Real estate | 2017 |
| Landsåshallen AS | Arts & recreation | 2021 |
| Landsåsveien Eiendom AS | Real estate | 2016 |
| Langmoan Næringspark AS | Real estate | 2014 |
| Langnesveien 16 Og 18 AS | Real estate | 2020 |
| Laro Invest AS | | 2024 |