| Hønefoss Nord Eiendomsutvikling AS | Real estate | 2008 |
| Hønefoss Nord Næringspark AS | Real estate | 2025 |
| Hønefoss Næringspark AS | Real estate | 2023 |
| Hønefoss Og Omegn Bygdeservice SA | Administrative & support | 2003 |
| Hønefoss Optiske AS | Wholesale & retail | 2007 |
| Hønefoss Radio - TV Service Ans | Other services | 1982 |
| Hønefoss Reisebyrå AS | Administrative & support | 1983 |
| Hønefoss Rørleggerbedrift AS | Construction | 1988 |
| Hønefoss Rørservice AS | Construction | 2025 |
| Hønefoss Specsavers AS | Wholesale & retail | 1996 |
| Hønefoss Stadion AS | Arts & recreation | 1999 |
| Hønefoss Steinhoggeri AS | Manufacturing | 2001 |
| Hønefoss Tak & Pipeservice AS | Construction | 2025 |
| Hønefoss Taxi SA | Transport & logistics | 1998 |
| Hønefoss Teknikk & Modellverksted Nuf | Professional & scientific | 2021 |
| Hønefoss Transport AS | Transport & logistics | 2020 |
| Hønefoss Ur Og Gull AS | Wholesale & retail | 2008 |
| Hønefoss Vaktselskap AS | Administrative & support | 2003 |
| Hønefoss Verktøifabrik AS | Real estate | 2005 |
| Hønefoss VVS AS | Construction | 2019 |
| Hønefoss VVS Holding AS | Construction | 2006 |
| Hønefoss Øyelegesenter AS | Health & social care | 2005 |
| Hønengata 72 AS | Real estate | 2016 |
| Hønengaten 77 / 79 Ans | Real estate | 1989 |
| Høyby Invest AS | Financial services | 2021 |
| Høymyr Hesteutstyr Avd. Ringerike AS | Wholesale & retail | 2025 |
| Høyt & Lavt AS | Construction | 2004 |
| Høyt & Lavt Holding AS | Construction | 2021 |
| Høyt & Lavt Utvikling AS | Real estate | 2016 |
| I.H.J Eiendom AS | Transport & logistics | 2012 |
| I.M.S.Teknikk AS | Manufacturing | 2024 |
| Ihp AS | Wholesale & retail | 2003 |
| Immensus AS | Professional & scientific | 2014 |
| Immensus Eiendom AS | Real estate | 2023 |
| Importservice Bil AS | Wholesale & retail | 2006 |
| Indre Havn Eiendom AS | Real estate | 1997 |
| Industri Og Va Service AS | Construction | 2014 |
| Inga Medne AS | | 2025 |
| Ingenium AS | Professional & scientific | 2025 |
| Ingeniør a Haukedalen AS | Professional & scientific | 2010 |
| Ingeniørselskapet Alfacon AS | Professional & scientific | 2007 |
| Ingosær AS | Financial services | 2018 |
| Innkjøp & Driftspartner AS | Administrative & support | 2004 |
| Innotech Norway AS | Professional & scientific | 2018 |
| Innovasjonsløft AS | Professional & scientific | 2017 |
| Insula Energikompetanse AS | Construction | 2018 |
| Intakt Bilskade Hønefoss AS | Other services | 2008 |
| Integra Eiendom AS | Real estate | 2026 |
| Integra Gruppen AS | | 2026 |
| Integra Helse AS | Health & social care | 2026 |
| INTERIØR24 AS | Wholesale & retail | 2016 |
| Involvate AS | Information & communication | 2024 |
| Ipg Intelligent Packaging Group AS | Wholesale & retail | 2014 |
| Isabella Cafe AS | Hospitality | 2023 |
| Iseveien AS | Real estate | 2005 |
| Ismajli Holdings AS | | 2025 |
| Ivar O Haugen Eiendom AS | Real estate | 1980 |
| J K Thorsens Patentbureau AS | Administrative & support | 1983 |
| J Lærum Holding AS | Real estate | 2022 |
| J. Holmby Holding AS | Real estate | 2024 |
| J. Skare AS | | 2026 |
| J.Fecadu Holding AS | | 2026 |
| J.Haaland Invest AS | | 2012 |
| Ja Invest 1 AS | | 2021 |
| Jan Lerfaldet AS | Manufacturing | 2016 |
| Jan's Eiendom AS | Construction | 2005 |
| Jarles Anleggstjenester AS | Construction | 2013 |
| Jarles Bil AS | Wholesale & retail | 2018 |
| Java Services AS | Professional & scientific | 2007 |
| JB Rekruttering Bemanning Rådgivning AS | Administrative & support | 2018 |
| JBK Vin AS | Wholesale & retail | 2012 |
| JBT Holding AS | Construction | 2016 |
| Jegtvolden Holding AS | | 2025 |
| Jensen Bygg Team AS | Construction | 1993 |
| Jensen Eiendomsutvikling AS | Real estate | 2005 |
| Jenshagen AS | | 2021 |
| Jensrud Import Ans | Wholesale & retail | 1989 |
| Jevnaker Butikkeiendom AS | Real estate | 2008 |
| Jevnaker Handelseiendom AS | Real estate | 2017 |
| JG Invest Ringerike AS | Real estate | 2016 |
| JH Haven AS | Professional & scientific | 2003 |
| JHB Invest AS | Real estate | 2016 |
| Jin Cheng Frukt & Grønt AS | Wholesale & retail | 2025 |
| Jinya Holding AS | | 2026 |
| JK Bang Holding AS | | 2021 |
| JK Service AS | Other services | 2013 |
| JM Dekor AS | Wholesale & retail | 2026 |
| Joakim Langset AS | Wholesale & retail | 2020 |
| Johan Tuft AS | Financial services | 2005 |
| Johanssons Auto AS | Wholesale & retail | 2011 |
| John Myrvang AS | Mining & quarrying | 1988 |
| Johnsrud Eiendom AS | Real estate | 2018 |
| Johnsrud Rør AS | Construction | 2024 |
| Jonn Skaar Service AS | Manufacturing | 2015 |
| Jordeshagen 4 AS | Real estate | 2010 |
| Jostimax AS | Professional & scientific | 2006 |
| Joto Eiendom Da | Real estate | 2000 |
| Joto Invest AS | | 2023 |
| JP Sandvold AS | Real estate | 2010 |
| JRH Eiendom AS | Real estate | 2018 |