| Ap Bygg AS | Construction | 2019 |
| Arbion Hønefoss Holding AS | Manufacturing | 2023 |
| Arbion Industries Hønefoss AS | Manufacturing | 2023 |
| Arena Kafe AS | Manufacturing | 2018 |
| Arguin AS | Financial services | 2005 |
| Ariadne Klinikken AS | Other services | 2020 |
| Arkimedum AS | Professional & scientific | 2014 |
| Arne Bach Eftf AS | Professional & scientific | 2001 |
| Arne G. Eiendom AS | Real estate | 2013 |
| Arne Holth Eiendom AS | Real estate | 2016 |
| Arne Mørch AS | Arts & recreation | 2011 |
| Arne's Ve Og Vel AS | Real estate | 2005 |
| Arnemannsveien 5 Hønefoss AS | Real estate | 2025 |
| Aronsen Bil AS | Wholesale & retail | 2019 |
| Art & Fun Norge AS | Financial services | 2005 |
| Arvegods AS | Real estate | 2020 |
| Arven Entreprenør AS | Real estate | 2026 |
| Arves Dekk AS | Wholesale & retail | 2026 |
| AS Ringerike Meieris Eiendomsselskap | Real estate | 1987 |
| AS Ringerikes Blad | Information & communication | 1919 |
| AS Sverregården | Real estate | 1975 |
| AS Tinn-Per | Manufacturing | 1965 |
| Asak AS | Manufacturing | 1991 |
| Asap Prosjekt AS | Professional & scientific | 2019 |
| Asbjørnsens Gate 19-21 AS | Real estate | 2021 |
| Asbjørnsensgate 12-14 AS | Real estate | 2014 |
| Asfaltering AS | Construction | 2018 |
| Ask Skogsdrift Da | Agriculture & fishing | 2001 |
| Askel Installasjon AS | Construction | 2005 |
| Askeladden Reiser AS | Administrative & support | 2002 |
| Askim Butikkeiendom AS | Real estate | 2019 |
| Askim Byggevarehus AS | Real estate | 2012 |
| Askseterveien Skogsbilveglag SA | Real estate | 2019 |
| Askveien 52 Da | Real estate | 2000 |
| Askveien 6 Hønefoss AS | Real estate | 2022 |
| Aslaksrud Holding AS | Construction | 2022 |
| Aspen Invest AS | Real estate | 2002 |
| Asta Eiendom AS | Real estate | 1947 |
| Atle Hestnes AS | Health & social care | 1994 |
| Atle Jensen Holding AS | Construction | 2005 |
| Audhumbla Ecosystem Engineering AS | Professional & scientific | 2019 |
| Auhaugen AS | | 2026 |
| Auksjonen Europa AS | Wholesale & retail | 2022 |
| Aurdal Butikkeiendom AS | Real estate | 2022 |
| Aureus Accounting AS | Professional & scientific | 2016 |
| Aurora Invest AS | Construction | 2013 |
| Austerheimvegen Butikkeiendom AS | Real estate | 2002 |
| Auto Invest Hønefoss | Wholesale & retail | 2023 |
| Auto-Assistanse AS | Transport & logistics | 1992 |
| Auto-Kompetanse AS | Wholesale & retail | 2018 |
| Autoconsult AS | Wholesale & retail | 2024 |
| Autohuset AS | Wholesale & retail | 2024 |
| Autolead AS | Information & communication | 2023 |
| Autosentralen AS | Real estate | 2022 |
| Av & På Elektro AS | Construction | 1996 |
| Avant Eiendomsutvikling AS | Real estate | 2003 |
| Averøy Handelsbygg AS | Real estate | 2010 |
| Aviation Defence Link AS | Professional & scientific | 2026 |
| Avika AS | Hospitality | 2021 |
| Avolain Technologies AS | Information & communication | 2023 |
| Azamat Ringerike BILPLEIE2 AS | Other services | 2025 |
| Azari Invest AS | Professional & scientific | 2016 |
| Azureit AS | Information & communication | 2019 |
| Aslaksrud Eiendom A/S | Real estate | 1988 |
| B Blystad Transport Ans | Transport & logistics | 1988 |
| B M Corner Ans | Wholesale & retail | 1990 |
| B&A Drift Da | Manufacturing | 2025 |
| B-Hip AS | Other services | 2018 |
| B.E. Gulsvik Holding AS | Real estate | 2005 |
| Baas Holding AS | Real estate | 2016 |
| Bakalao AS | Professional & scientific | 2010 |
| Bakketun Invest AS | Real estate | 2005 |
| Bakåsen AS | Real estate | 1992 |
| Baldertech AS | Professional & scientific | 2007 |
| Ballari Rindal AS | Real estate | 2005 |
| Baltic Renewables AS | Energy | 2023 |
| Bamble Handelsbygg AS | Real estate | 2006 |
| Banda Ringerike AS | Wholesale & retail | 2012 |
| Banggren & Stadheim Eiendom AS | | 2025 |
| Banggren Bil AS | Wholesale & retail | 2023 |
| Bangkokk AS | Hospitality | 2020 |
| Barbroveien 2 AS | Real estate | 2017 |
| Barbroveien Butikkeiendom AS | Real estate | 2005 |
| Bardufoss Handelseiendom AS | Real estate | 2010 |
| Bare Biler AS | Wholesale & retail | 2018 |
| Bare Lek AS | Wholesale & retail | 2021 |
| Baredekk AS | Wholesale & retail | 2014 |
| Barman Hanssen AS | Information & communication | 1996 |
| Barman Hanssen Invest AS | Real estate | 2006 |
| BDR Eiendom AS | Real estate | 1982 |
| Be Still AS | Transport & logistics | 2021 |
| Beauty by Mi - Skjønnhet Og Velvære AS | Other services | 2022 |
| Beauty Studio GN AS | Other services | 2021 |
| Bech Eiendom Da | Real estate | 2004 |
| Beform Norge AS | Manufacturing | 1987 |
| Bekker Smaa AS | | 2025 |
| Bekkestad Capital AS | Real estate | 2004 |
| Belcan AS | Professional & scientific | 2015 |
| Bemanningstjenester AS | Administrative & support | 2023 |
| Bemela AS | | 2025 |