| Klein Boligeiendom 2 AS | Real estate | 2016 |
| Klein Boligeiendom 3 AS | Real estate | 2016 |
| Klein Boligeiendom 4 AS | Real estate | 2017 |
| Klein Boligeiendom 5 AS | Real estate | 2019 |
| Klein Boligeiendom 6 AS | Real estate | 2019 |
| Klein Boligeiendom 7 AS | Real estate | 2019 |
| Klein Boligeiendom 8 AS | Real estate | 2020 |
| Klein Boligeiendom 9 AS | Real estate | 2020 |
| Klein Boligeiendom AS | Real estate | 2013 |
| Klein Capital AS | Professional & scientific | 2020 |
| Klein Consulting AS | Professional & scientific | 2020 |
| Klein Eiendom AS | Real estate | 2016 |
| Klein Group AS | Professional & scientific | 2021 |
| Klein Invest AS | Real estate | 2014 |
| Klein Næringseiendom AS | Real estate | 1998 |
| Kleivanveien 15 AS | Construction | 2012 |
| Kleivbakken 9 AS | Real estate | 2018 |
| Kleivco AS | Professional & scientific | 2024 |
| Kleiven Kultur, Kraftsang Og Keyboard AS | Arts & recreation | 2022 |
| Kleivstad AS | Administrative & support | 2026 |
| Kleivveien Holding AS | Real estate | 2021 |
| Kleivveien Næring AS | Real estate | 2018 |
| Kleivveien Parkering AS | Real estate | 2021 |
| Kleivveien Utbygging AS | Real estate | 2015 |
| Kleivveien Utvikling AS | | 2020 |
| Klekken AS | Wholesale & retail | 2009 |
| Klekken Holding AS | Real estate | 2022 |
| Klekkensvingen AS | | 2022 |
| Klem Holding AS | Professional & scientific | 2018 |
| Klemetsrud AS | Professional & scientific | 2021 |
| Klemetsrud Drift AS | Wholesale & retail | 2026 |
| Klemetsrud Dyreklinikk AS | Professional & scientific | 2018 |
| Klemetsrud Eiendom AS | Real estate | 2021 |
| Klemetsrud Grave Og Sprengeservice AS | Construction | 2015 |
| Klemetsrud Holding AS | Real estate | 2021 |
| Klemetsrud Invest AS | Manufacturing | 2011 |
| Klemp Invest AS | | 2021 |
| Klems AS | Financial services | 2012 |
| Klems Gate 29 AS | Real estate | 2013 |
| Klepland Næring AS | Real estate | 2018 |
| Kleppan & Wessel Holding AS | | 2013 |
| Kleppe Group AS | Information & communication | 2025 |
| Klerti AS | Wholesale & retail | 2023 |
| Kles-Kroken Da | Other services | 2008 |
| Kleve Holding AS | Professional & scientific | 2026 |
| Kleven Bergersen Og Michelsen Invest Ans | | 1989 |
| Kleven Forvaltning AS | | 2024 |
| Kleven Prosjekt 401 AS | | 2001 |
| Klevenstern AS | Real estate | 2004 |
| Klever & Backe AS | Real estate | 2013 |
| Klever Eiendom AS | Real estate | 2016 |
| Klever Holding AS | | 2020 |
| Klever Invest AS | | 2018 |
| Klevgaten 1 AS | Real estate | 2015 |
| Klevgaten Utvikling AS | Real estate | 2019 |
| Klevjer Invest AS | | 2021 |
| KLF Art AS | Wholesale & retail | 2020 |
| KLF AS | Real estate | 2008 |
| KLF Invest AS | Wholesale & retail | 2005 |
| KLF Servicekontor AS | Professional & scientific | 2016 |
| Kliché AS | Professional & scientific | 2024 |
| Klientbooking AS | Professional & scientific | 2025 |
| Klifur Da | Education | 2026 |
| Klikk Det AS | Professional & scientific | 2023 |
| KLIKK9 Da | Arts & recreation | 2025 |
| Klikka Banan AS | | 2025 |
| Klima Og Bygg AS | Construction | 2005 |
| Klima Og Bygg Eiendom AS | Real estate | 2017 |
| Klima Og Bygg Holding AS | Construction | 2020 |
| Klimaantropologen AS | Professional & scientific | 2024 |
| Klimaeksperten AS | Administrative & support | 2025 |
| Klimakompetanse AS | Construction | 2012 |
| Klimaq AS | Wholesale & retail | 2024 |
| Klimaservice Og Transport AS | Construction | 2012 |
| Klimaservice Oslo AS | Construction | 2015 |
| Klimateknikk Oslo AS | Construction | 2004 |
| Klimato AS | Information & communication | 2019 |
| Klingande Song AS | Arts & recreation | 2021 |
| Klingen Daams Holding AS | Administrative & support | 2005 |
| Klingenberg Bardrift AS | Hospitality | 2019 |
| Klingenberg Holding AS | Wholesale & retail | 2024 |
| Klingenberggaten 4 AS | Real estate | 1996 |
| Klingenberggaten 5 AS | Real estate | 1985 |
| Klingenberggaten 7 Da | Real estate | 1990 |
| Klingit Norway AS | Information & communication | 2015 |
| Klingspor Norsk Avdeling Av Utenlandsk Foretak Nuf | Wholesale & retail | 2000 |
| Klingzell Gulv AS | Construction | 2025 |
| Klinikk 10 a Ans | Health & social care | 2003 |
| Klinikk a AS | Health & social care | 2021 |
| Klinikk Alekna AS | Health & social care | 2016 |
| Klinikk Amalie AS | Other services | 2026 |
| Klinikk Fjeld AS | Education | 2006 |
| Klinikk for Fysikalsk Aromaterapi Da | Health & social care | 2007 |
| Klinikk for Fysioterapi Og Manuellterapi AS | Health & social care | 2018 |
| Klinikk for Smertebehandling AS | Health & social care | 2005 |
| Klinikk Friske Muskler AS | Health & social care | 2021 |
| Klinikk Frogner AS | Health & social care | 2005 |
| Klinikk Frogner Holding AS | Health & social care | 2020 |
| Klinikk Groruddalen AS | Health & social care | 2008 |
| Klinikk My Moment AS | Other services | 2026 |