| Arvan AS | Information & communication | 2018 |
| Arvarius AS | Real estate | 1987 |
| Arve Johansson Invest AS | Real estate | 2005 |
| ARVE-2 AS | Financial services | 2004 |
| Arveco AS | | 2015 |
| Arvel AS | Real estate | 1996 |
| Arvesen Eiendomskonsult AS | Real estate | 2014 |
| Arvesølvet Invest AS | Financial services | 2017 |
| Arvia Holding AS | | 2023 |
| Arvid Nilsson Norge AS | Wholesale & retail | 1990 |
| Arvid Nordquist Norge AS | Wholesale & retail | 2002 |
| Arvid Nyholm AS | Professional & scientific | 2024 |
| Arvidsson-Monge AS | Wholesale & retail | 2021 |
| Arvika Kakel & Interiør AB | Construction | 2000 |
| Arvin Privatundervisning AS | Real estate | 2015 |
| Arvo Holding AS | | 2025 |
| Arvo Invest AS | Real estate | 1972 |
| Arvo Kontorfelleskap AS | Real estate | 2025 |
| Arx Compliance AS | Information & communication | 2023 |
| Arxteon AS | Professional & scientific | 2026 |
| Arxx Therapeutics AS | Professional & scientific | 2015 |
| Ary AS | Arts & recreation | 2018 |
| Arya Invest AS | | 2017 |
| Aryo AS | Hospitality | 2020 |
| Aröd AS | Financial services | 2017 |
| AS & AS Holding AS | Construction | 2022 |
| AS 3S - System Software Services | | 2005 |
| AS Aasen Garasjelag | Real estate | 1964 |
| AS Abakhus | | 2018 |
| AS Adams Express Eiendom | Real estate | 1898 |
| AS Adamstuen Bygning III | Households | 1934 |
| AS Adamstuen Bygning IV | Households | 1936 |
| AS Aegeus | Real estate | 1905 |
| AS Aircontact | Transport & logistics | 1962 |
| AS Airtour Holding | Financial services | 1976 |
| AS Akersgaten 7 & 9 | Real estate | 1914 |
| AS Akkumula | Real estate | 1961 |
| AS Aldersboliger for Læger | Real estate | 1960 |
| AS Ammerud Varmesentral | Energy | 1969 |
| AS Amtmann Meinichs Gate 20 | Households | 1940 |
| AS Anakonda | Transport & logistics | 2006 |
| AS Anja | Financial services | 1979 |
| AS Apotekernes Hus | Professional & scientific | 1934 |
| AS Arbeidernes Bygge-Compagni III | Households | 1936 |
| AS Argentario | Administrative & support | 1988 |
| AS Arkitektenes Hus | Real estate | 1956 |
| AS Atlantic Invest | Real estate | 1987 |
| AS Atlantic Oil & Investment Co | Real estate | 1902 |
| AS Atnestua | Real estate | 1924 |
| AS Audley | Transport & logistics | 1960 |
| AS Aurskoggaten Boligbygg | Households | 1949 |
| AS Automax | Wholesale & retail | 1980 |
| AS B N M | Wholesale & retail | 1938 |
| AS B'Zeos | Professional & scientific | 2018 |
| AS Baldersgate 4 | Households | 1940 |
| AS Balkeby | Households | 1936 |
| AS Balkongbygg | Construction | 1993 |
| AS Banan | Real estate | 1923 |
| AS Bauer GmbH | Health & social care | 2009 |
| AS Begraf | Information & communication | 1969 |
| AS Bemacs | Real estate | 1961 |
| AS Bennechesgate 1 Og 3 | Households | 1928 |
| AS Bentsebrugata 25 | Households | 1938 |
| AS Bergbu | Real estate | 1912 |
| AS Bergensgaten 13 | Households | 1914 |
| AS Bergensveien Byggeselskap | Households | 1951 |
| AS Bergsliens Gate 11 | Households | 1926 |
| AS Bertilia | Real estate | 1929 |
| AS Bidne | | 2022 |
| AS Bislet Bilutleie | Administrative & support | 1989 |
| AS Bjerke Tomteselskap | Financial services | 1986 |
| AS Bjerregaards Gate 68 | Households | 1931 |
| AS Bjerregaardsgate 31 | Households | 1939 |
| AS Bjerregårdsg 37 | Households | 1947 |
| AS Bjørn Investor | Real estate | 1993 |
| AS Blaasenborg Pilestredet 86/88 | Households | 1975 |
| AS Bogstadveien 3 & 5 | Households | 1916 |
| AS Bogstadveien 30 Byggeselskap | Real estate | 1950 |
| AS Bogstadveien 34 | Real estate | 1938 |
| AS Bogstadveiens Skotøiforretning | Real estate | 1914 |
| AS Brageveien 3 | Real estate | 1927 |
| AS Brandts Gate 2 | Households | 1934 |
| AS BRANNFJELLVEIEN 96 og 98 | Real estate | 1953 |
| AS Brdr Michaelsen Avd I Norge | Wholesale & retail | 1956 |
| AS Brustad Eiendom | Real estate | 1989 |
| AS Bukefalos | Financial services | 1973 |
| AS Bygdø Alle 111 | Real estate | 1954 |
| AS Bygdø Alle 123 | Households | 1954 |
| AS Bygdø Alle 127 | Households | 1956 |
| AS Bygdø Alle 23 | Real estate | 1960 |
| AS Bygdø Alle 57 | Households | 1924 |
| AS Bygdø Alle 66 | Households | 1929 |
| AS Bygdø Alle 75 | Households | 1932 |
| AS Bygdøy Alle 70 | Real estate | 1930 |
| AS Bygganalyse | Professional & scientific | 1986 |
| AS Bedriftsrådgivning og- utvikling | Professional & scientific | 1987 |
| AS BioTrade | Health & social care | 1989 |
| AS Bo | Real estate | 1941 |
| AS Bogstadveien 29 | Real estate | 1917 |
| AS Bogstadveien 30 | Real estate | 1912 |