| Antons Eiendom AS | Real estate | 1978 |
| Anvalda Norge AS | Construction | 2020 |
| Anwe Holding AS | Professional & scientific | 2017 |
| Anwima AS | Real estate | 2017 |
| Anygaard AS | | 2025 |
| Aod IT AS | Information & communication | 2011 |
| Ap Finans Og Invest AS | Real estate | 2005 |
| Aparte Vin AS | Wholesale & retail | 2021 |
| Apex Automobiles AS | Wholesale & retail | 2013 |
| Apex Solution AS | Professional & scientific | 2024 |
| Apia AS | Financial services | 2010 |
| Aply AS | Professional & scientific | 2023 |
| Apolo Bygg AS | Construction | 2025 |
| Apotekdrift Helseparken AS | Wholesale & retail | 2024 |
| Apoteket Strømsø AS | Wholesale & retail | 2018 |
| Apoteket Union Brygge AS | Wholesale & retail | 2013 |
| APP1 AS | Information & communication | 2021 |
| Appell Consult AS | Professional & scientific | 2026 |
| Appell Reklamebyrå AS | Professional & scientific | 1999 |
| Applirank Software AS | Information & communication | 2025 |
| Aprego AS | Professional & scientific | 2023 |
| Aqua Femme AS | Wholesale & retail | 2001 |
| Aquaflow AS | Wholesale & retail | 2018 |
| Aradas AS | Wholesale & retail | 2018 |
| Aragon Holding AS | Real estate | 1999 |
| Arand AS | Financial services | 2005 |
| Arbeidergata 10-12 AS | Real estate | 2018 |
| Arbeidergata 17 AS | Real estate | 2002 |
| Arbeidergaten 6 Eiendom AS | Real estate | 2014 |
| Arbo Eiendom AS | Real estate | 1991 |
| Arbo Entreprenør AS | Construction | 1993 |
| Arbo Utvikling AS | Real estate | 2019 |
| Arboris Holding AS | | 2025 |
| Archean Core AS | Wholesale & retail | 2021 |
| Arcitura Eiendom AS | Real estate | 2022 |
| Arcium Asker AS | Real estate | 2026 |
| Arcium Bolig AS | Real estate | 2005 |
| Arco Bygg&Rør AS | Construction | 2018 |
| Arco Interpharma AS | Wholesale & retail | 1977 |
| Arcom AS | | 2006 |
| Arcteec Invest AS | Arts & recreation | 2018 |
| Arctic Labradoodles AS | Agriculture & fishing | 2011 |
| Arctic Memory AS | Financial services | 2018 |
| Arctic Records Da | Arts & recreation | 1996 |
| Arctic Royal AS | Wholesale & retail | 2026 |
| Arctic World Archive AS | Information & communication | 2023 |
| Arctis Eiendom AS | | 1999 |
| Ard Group AS | Wholesale & retail | 2012 |
| Areal Entreprenør AS | Construction | 2019 |
| Areal Nor AS | Real estate | 2012 |
| Areal Viken AS | Real estate | 2009 |
| Arealplan AS | Wholesale & retail | 2013 |
| Arealplan Utvikling AS | Real estate | 2022 |
| Arena Bil Og Bilpleie AS | Wholesale & retail | 2013 |
| Arenabre AS | Health & social care | 2022 |
| Arentz Holding AS | Professional & scientific | 2005 |
| Ares Holding AS | Arts & recreation | 2024 |
| Arhaus Eiendom AS | Manufacturing | 2021 |
| Arhaus Pro Bygg AS | Construction | 2021 |
| Ari Barbershop AS | Other services | 2023 |
| Arise AS | Professional & scientific | 2023 |
| Arka Holdning AS | | 2026 |
| Arkato Eiendom AS | Real estate | 1978 |
| Arken Økonomitjenester AS | Professional & scientific | 1997 |
| Arkitektgruppen Drammen AS | Professional & scientific | 1997 |
| Arkitektkompaniet AS | Professional & scientific | 1985 |
| Arkitektkontoret Hauger AS | Professional & scientific | 2015 |
| Arkitektkontoret Nils Tveit AS | Professional & scientific | 1991 |
| Arkon Entreprenør AS | Real estate | 2026 |
| Arlberg Invest AS | Real estate | 2022 |
| Armand Skjønnhaug Holding AS | | 2025 |
| Arne Skarra AS | Wholesale & retail | 2012 |
| Arnebrott Holding AS | | 2026 |
| Arnesen Kapital Holding AS | Professional & scientific | 2025 |
| Arnesen Utvikling AS | | 1994 |
| Aroma Foods AS | Manufacturing | 2012 |
| Aron Forvaltning AS | | 2005 |
| Art Travel AS | Administrative & support | 1998 |
| Artea Malermester Drammen AS | Construction | 2026 |
| Artefakt AS | | 2019 |
| Arthurson Holding AS | Professional & scientific | 2018 |
| Artia Regnskap AS | Professional & scientific | 2025 |
| Artist Vision Management AS | Professional & scientific | 2024 |
| Artist Vision Nuf | Professional & scientific | 2007 |
| Artist Vision Publishing AS | Information & communication | 2015 |
| Artistportalen AS | Professional & scientific | 2014 |
| Arupsgate 18 Parkering AS | Real estate | 2008 |
| Arvans Holdingselskap AS | Wholesale & retail | 2017 |
| Arvans Invest AS | Wholesale & retail | 2023 |
| Arx Innovation AS | Information & communication | 1998 |
| Arya Eiendom AS | Real estate | 2018 |
| AS Ariel Invest | Real estate | 2022 |
| AS Boni | Construction | 2005 |
| AS Danvikgt 3 | Households | 1950 |
| AS Druidenes Hus | Real estate | 1972 |
| AS Eiendomsformidling | Real estate | 1974 |
| AS Kellox | Wholesale & retail | 2002 |
| AS Konnerudgaten 16 | Households | 1953 |
| AS Lærumsgt 6 | Households | 1949 |
| AS Obas | Real estate | 2001 |