| Correlator AS | Ski | 2013 |
| Correzione Forvaltning AS | Dokka | 2022 |
| Corrmatec AS | Fornebu | 2016 |
| Corroteam AS | Tranby | 1983 |
| Corsitec AS | Kristiansand S | 2011 |
| Cort Piil Consultant AS | Nesttun | 2013 |
| Cortavik AS | Haslum | 2020 |
| Cortech AS | Bekkjarvik | 2024 |
| Corticalis AS | Oslo | 2006 |
| Corum Holding AS | Hjelset | 2013 |
| Corvina AS | Sortland | 2021 |
| Corvus Accounting AS | Oslo | 1996 |
| Corvus Energy Fuel Cell AS | Nesttun | 2023 |
| Cosentino Norway AS | Vestby | 2012 |
| Cosl Rig Ltd | Sandnes | 2007 |
| Cosmic Capital AS | Haslum | 2023 |
| Cosmion Consulting AS | Halden | 2026 |
| Cosmo AS | Oslo | 2013 |
| Cosmoneering AS | Lillesand | 2020 |
| Cosmos Construction Nuf | 02190 Naujininkai, Vilnius | 2015 |
| Cosmos Holding AS | Lillesand | 2020 |
| Cosmos Invest AS | Tverrelvdalen | 2014 |
| Cost Consult Norway AS | Ski | 2016 |
| Cost Ctrl AS | Holmestrand | 2017 |
| Cost Partner Group AS | Oslo | 2010 |
| Cost Partner Norge AS | Oslo | 2017 |
| Cost Reduction Management AS | Oslo | 2014 |
| Cost Technology AS | Høvik | 1990 |
| Cost Økonomi AS | Saksvik | 2025 |
| Costa a AS | Trondheim | 2025 |
| Costtracker AS | Oslo | 2016 |
| Così Consult AS | Tunhovd | 2007 |
| Cotec Medieteknikk AS | Bergen | 2015 |
| Cotech AS | Alvdal | 1990 |
| Cotecna Inspection | 1207 Geneva | 2017 |
| Cotopaxi AS | Oslo | 2020 |
| Cottonwood Advisory AS | Moss | 2023 |
| Cottonwood Holding AS | Moss | 2023 |
| Couleur AS | Oslo | 2020 |
| Counterculture Partnership Norway Nuf | Tn40 1Hh | 2020 |
| Countmatters AS | Ski | 1989 |
| Countmatters Group AS | Ski | 2006 |
| Countryartists International AS | Froland | 2001 |
| Coupler Holding AS | Oslo | 2020 |
| Covance Clinical and Periapproval Services | Oslo | 1997 |
| Covartec AS | Fyllingsdalen | 2018 |
| Cove and Cooper AS | Hafrsfjord | 2026 |
| Cove Bay Drilling Fluids Ltd | Aberdeen Ab12 3Sl Scotland | 2021 |
| Covent Garden AS | Billingstad | 1998 |
| Cover Arkitektverksted AS | Oslo | 2005 |
| Cover Consult AS | Oslo | 2022 |
| Covered Consulting AS | Oslo | 2016 |
| Coverskin AS | Os | 2025 |
| Coverwind Solutions S.L.U | Es-36003 Pontevedra | 2021 |
| Covet Oslo AS | Oslo | 2026 |
| Covey Network AS | Nøtterøy | 2023 |
| Covfefe AS | Bergen | 2017 |
| Cowaso AS | Trondheim | 2025 |
| Cowex A/S Nuf | Dk-3770 Tejn | 2025 |
| Cowi | Dk-2800 Kongens Lyngby | 2013 |
| Cowi AB | Se-411 04 Göteborg | 2013 |
| Cowi AS | Oslo | 1997 |
| Cowi Holding | Dk-2800 Kgs.Lyngby | 2023 |
| Cowi India | In-122016 Gorgaon Haryana | 2021 |
| Cowintech Co.Ltd | 31409 Chungcheongnan-Do | 2023 |
| Cowo AS | Rådal | 2015 |
| Coworx AS | Kristiansand S | 2015 |
| Cowry Ev AS | Oslo | 2018 |
| Cox Consulting AS | Namsos | 2026 |
| Cox Strategisk Design AS | Trondheim | 1997 |
| Coxit AS | Oslo | 2005 |
| Coxnes AS | Rovde | 2012 |
| Cozy Design AS | Elverum | 2024 |
| CP Konsulent Og Rådgivning AS | Oslo | 2024 |
| CPC (GB) Ltd | Aberdeenshire Ab31 5Zg | 2011 |
| Cperfect AS | Oslo | 2020 |
| Cpi Chiron Acquisition AS | Trondheim | 2023 |
| CPM Analytics AS | Oslo | 2006 |
| CPM AS | Bygland | 2021 |
| CPM Industrial Ltd | Glasgow G3 6Ef Scotland | 2020 |
| Cpmaterials AS | Søgne | 2014 |
| Cpoint AS | Rådal | 2004 |
| CPT Technical Services Ltd | Gb-Devon Pl6 8En | 2019 |
| CQ Arctic AS | Stavanger | 2018 |
| CQ Consult AS | Haslum | 2026 |
| Cqrts AS | Oslo | 2011 |
| CR Group AS | Skien | 2011 |
| CR Holding AS | Nesbru | 1997 |
| CR Organisasjons Support AS | Kongsvinger | 2014 |
| CR Regnskap AS | Drammen | 1988 |
| CR Rådgivning AS | Bergen | 2013 |
| Cr'Emanilsen AS | Spillum | 2024 |
| CR1.NO AS | Kabelvåg | 2015 |
| Cra International (Norway) AS | Oslo | 2017 |
| Cra Offshore Limited | Hebburn Ne31 1Rs, Tyne & Wear | 2019 |
| Cradle AS | Oslo | 2026 |
| Craft Consulting AS | Steinsland | 2020 |
| Craft Products Ltd AS | Eidsnes | 2000 |
| Crafting House AS | Oslo | 2010 |
| Craig Smith Offshore Ltd | Aberdeen Ab24 1Rg | 2019 |