| Blomsøs Eiendomsselskap AS | Real estate | 1994 |
| Bluecrew AS | Administrative & support | 2025 |
| Blå Hav AS | Professional & scientific | 2020 |
| Blåfjelle AS | Health & social care | 2018 |
| Blåhatten AS | Information & communication | 2025 |
| Blått Hav Eiendom AS | Real estate | 2010 |
| Blått Hav Holding AS | Health & social care | 2010 |
| BNH Eiendom AS | Wholesale & retail | 1999 |
| Bogstrand AS | Construction | 2010 |
| Boinor AS | Real estate | 2002 |
| Bonanza Beauty AS | Other services | 2021 |
| Bonovo Bygg AS | Construction | 2024 |
| Bonovo Consult AS | Professional & scientific | 2024 |
| Bonovo Eiendom AS | Real estate | 2024 |
| Bonovo Gruppen AS | Construction | 2024 |
| Bor. Fysioterapi AS | Health & social care | 2004 |
| Boreal Aurora Sail & Sea AS | | 2026 |
| Borealis Finans 2 AS | Real estate | 2018 |
| Bornø AS | Administrative & support | 2021 |
| Brajobba Bygg AS | Construction | 2025 |
| Brannpro AS | Construction | 2022 |
| Bratco AS | Real estate | 2014 |
| Bratol Invest AS | | 2026 |
| Bratteng Holding AS | | 2021 |
| Brebo AS | Real estate | 2023 |
| Breimo Invest AS | Real estate | 2009 |
| Breivika Dagligvarer AS | Wholesale & retail | 2020 |
| Brga AS | Hospitality | 2017 |
| Brom Thermo AS | Wholesale & retail | 2026 |
| Brovingen Utvikling AS | Real estate | 2017 |
| Bryggekafeen På Grøtavær Da | Hospitality | 2026 |
| Brødrene Finstad AS | Administrative & support | 2014 |
| Brødrene Killi AS | Construction | 2000 |
| Bsørensen Holding AS | | 2023 |
| BT Vin AS | Hospitality | 2026 |
| Bt-Harstad Eiendom AS | Real estate | 2019 |
| Bt-Harstad Holding AS | Construction | 2018 |
| BTT AS | Real estate | 2005 |
| Bunadsstua Harstad AS | Manufacturing | 2005 |
| Bunadsøm Harstad AS | Manufacturing | 2016 |
| By Stine Svendsen AS | Other services | 2025 |
| Bybirgithe AS | Other services | 2017 |
| Bygg Eng Eiendom AS | Real estate | 2017 |
| Byggemestrene Kristensen & Linløkken AS | Construction | 1988 |
| Byggesystemer AS | | 2023 |
| Byggmester Rune Hansen AS | Construction | 2025 |
| Byggsikkerhet AS | Professional & scientific | 2003 |
| Byggteam Harstad AS | Construction | 2019 |
| Bygningstakst AS | Professional & scientific | 2005 |
| Byparkering AS | Real estate | 2011 |
| Byterminalen AS | Real estate | 1994 |
| Bårnakkvn 1 AS | Real estate | 1998 |
| Båt Og Motorservice AS | Transport & logistics | 1984 |
| Båt- Og Industriservice AS | Manufacturing | 2004 |
| Bøndernes Regnskapslag Arl SA | Professional & scientific | 1970 |
| C.Boquist AS | Professional & scientific | 2023 |
| Calma Tannklinikk AS | Health & social care | 2019 |
| Campetter AS | Professional & scientific | 2024 |
| Candles With a Kick AS | Wholesale & retail | 2022 |
| Capitano AS | Administrative & support | 2016 |
| Cargo Team AS | Transport & logistics | 2017 |
| Carina Skarsem AS | Other services | 2025 |
| Carizma Velvære AS | | 2026 |
| Caron AS | Wholesale & retail | 2021 |
| Caron Autoservice AS | Other services | 2026 |
| Carpe Diem Da | Hospitality | 1993 |
| CARS2GO AS | Wholesale & retail | 2012 |
| Casa Gunn AS | Wholesale & retail | 2026 |
| Cefo & Partners AS | Wholesale & retail | 2014 |
| Cefo Eiendom AS | Real estate | 1994 |
| Cefo Invest AS | Professional & scientific | 1994 |
| Cefo Tech AS | Administrative & support | 2026 |
| Ceil AS | Information & communication | 2026 |
| Ceil Invest AS | | 2026 |
| Cejls Eiendom AS | Real estate | 2011 |
| Celeste Hair Design AS | Other services | 2005 |
| Celko AS | Wholesale & retail | 2012 |
| Cetus Invest AS | Professional & scientific | 2005 |
| Changeneering AS | Professional & scientific | 2023 |
| Charlotte Dyreklinikk AS | Professional & scientific | 2026 |
| Chase GT AS | Information & communication | 2025 |
| Chicago Hope AS | Real estate | 2012 |
| Chickenhouse Harstad AS | Hospitality | 2017 |
| Chili Harstad AS | Professional & scientific | 1998 |
| Chili Holding AS | Professional & scientific | 2004 |
| Christensen Transport Vestbygd AS | Transport & logistics | 2005 |
| Christiane Wulff AS | Manufacturing | 2010 |
| Chro Holding AS | Real estate | 2022 |
| Cloudberry HLD AS | | 2026 |
| Cloudsource AS | Professional & scientific | 2010 |
| Comfort Harstad AS | Construction | 2008 |
| Communicare AS | Professional & scientific | 2013 |
| Compartner Eiendom AS | Real estate | 2012 |
| Competo Consulting AS | Information & communication | 2016 |
| Completion Tracer AS | Professional & scientific | 2022 |
| Comstation AS | Information & communication | 2020 |
| Coneco AS | Administrative & support | 2014 |
| Confi AS | Professional & scientific | 2020 |
| Contrasto AS | Administrative & support | 2016 |
| Copysafe AS | Wholesale & retail | 2016 |