| Attache AS | Professional & scientific | 2024 |
| Attano AS | Professional & scientific | 2025 |
| Attaxo AS | Real estate | 2006 |
| Attelega Holding AS | Professional & scientific | 2025 |
| Atten 36 AS | Real estate | 2008 |
| Atten:Atten AS | | 2017 |
| Attend IT AS | Information & communication | 2006 |
| Attendo AS | Professional & scientific | 2019 |
| Attendo Norge AS | Health & social care | 1997 |
| Attends AS | Wholesale & retail | 1999 |
| Attensi AS | Information & communication | 2009 |
| Attensi Holding AS | | 2025 |
| Attention Management AS | Financial services | 1998 |
| Attention Reklamebyrå AS | Professional & scientific | 2006 |
| Attenzione AS | Professional & scientific | 2019 |
| Attest Da | Professional & scientific | 2010 |
| Attho Invest AS | | 2021 |
| Attia AS | Information & communication | 2026 |
| Attico Studio AS | Professional & scientific | 2023 |
| Attika AS | Real estate | 2022 |
| Attistiba AS | Real estate | 2022 |
| Attitude AS | Other services | 2015 |
| Attitunes Da | Arts & recreation | 2017 |
| Attityd Holding AS | | 2026 |
| Attivo AS | Real estate | 2015 |
| Attivo Bolig Brekkeveien AS | Real estate | 2021 |
| Attivo Bolig Brekkeveien Holding AS | Real estate | 2023 |
| Attivo Bolig Hektneråsen AS | Real estate | 2023 |
| Attivo Bolig Lambertseter AS | Real estate | 2021 |
| Attivo Bolig Landingsveien Holding AS | Real estate | 2023 |
| Attivo Bolig Sørumsand AS | Real estate | 2021 |
| Attivo Eiendomsutvikling II AS | Real estate | 2016 |
| Attivo Eiendomsutvikling III AS | Real estate | 2018 |
| Attivo Næring Brekkeveien AS | Real estate | 2024 |
| Attivo Næring Kjelsås AS | Real estate | 2018 |
| Attivo Næring Lambertseter AS | Real estate | 2004 |
| Attly AS | Information & communication | 2025 |
| Attme Åne AS | Real estate | 2007 |
| Attraqua Specific Baits AS | Agriculture & fishing | 2015 |
| Atvantic & Co. AS | Professional & scientific | 2023 |
| Atvantic Partners Nordic Nuf | Information & communication | 2022 |
| Atvenge Holding AS | | 2016 |
| Atventure AS | Professional & scientific | 2014 |
| Atvexa AS | | 2022 |
| Atw Capital AS | | 2024 |
| Atwater AS | Real estate | 2019 |
| Atxineta Holdings AS | | 2020 |
| Atyp AS | Professional & scientific | 2019 |
| Atyp Holding AS | Professional & scientific | 2019 |
| Au Naturel (UK) Inc Norway Nuf | Wholesale & retail | 2007 |
| Aua Holdning AS | | 2024 |
| Auan AS | Health & social care | 2003 |
| Aubel Investments AS | Professional & scientific | 2008 |
| Aubert Geo-Services AS | Financial services | 2015 |
| Aubert Kapital AS | Professional & scientific | 2022 |
| Aubert Vekst AS | Financial services | 1997 |
| Aubrey AS | Information & communication | 2025 |
| Auco AS | Information & communication | 2024 |
| Auco Holding AS | | 2024 |
| Aucthan AS | Real estate | 2021 |
| Auctor Security AS | Administrative & support | 2023 |
| Auctoritas AS | Real estate | 1998 |
| Auctus AS | Real estate | 2017 |
| Auctus Cap AS | | 2024 |
| Auctus Holding AS | | 1987 |
| Auctus Management AS | Real estate | 2001 |
| Aud Aasbo AS | Education | 2018 |
| Audacia AS | | 2024 |
| Audacter AS | Information & communication | 2022 |
| Audax Design Og Eiendom Da | Real estate | 2010 |
| Audendum AS | | 2021 |
| Audens AS | Professional & scientific | 2025 |
| Audeo AS | Professional & scientific | 2012 |
| Audere AS | Information & communication | 2015 |
| Audere Holding AS | Professional & scientific | 2021 |
| Audhumla Ans | Administrative & support | 2000 |
| Audio Import AS | Wholesale & retail | 2018 |
| Audiocare Solutions AS | Professional & scientific | 2024 |
| Audiopedagog Evelina Larsson AS | Health & social care | 2022 |
| Audiopedagog Guri Engernes Nielsen AS | Health & social care | 2014 |
| Audiopedagogene AS | Health & social care | 2025 |
| Audiophone Limited | Wholesale & retail | 2018 |
| Audioplus Oslo AS | Health & social care | 2022 |
| Audite AS | Professional & scientific | 2017 |
| Audite Holding AS | | 2021 |
| Auditorium AS | Arts & recreation | 1985 |
| Audly AS | Professional & scientific | 2013 |
| Audra AS | Professional & scientific | 2026 |
| Audriusholding AS | Construction | 2025 |
| Audun Agnar Music AS | Arts & recreation | 2024 |
| Audun Collection AS | Administrative & support | 2026 |
| Audun Føyen AS | Information & communication | 2017 |
| Audun Investerer AS | Information & communication | 2021 |
| Audun Mathias Øygard Holding AS | | 2020 |
| Audunarhus Invest AS | Real estate | 2021 |
| Audunsand Holding AS | | 2019 |
| Auestad Automation AS | Professional & scientific | 2025 |
| Auge Holding AS | | 2026 |
| Auge Labs AS | Information & communication | 2026 |
| Augea AS | Wholesale & retail | 2023 |