| Bredero Shaw (Malaysia) SDN. Berhad | My-25720 Kuantan Pahang | 2021 |
| Breivik Kalkverk AS | Larsnes | 1999 |
| Brekka Sandtak AS | Grimstad | 2002 |
| Brekke Stenbrudd Nuf | Halden | 2006 |
| Bremanger Aggregates AS | Svelgen | 1998 |
| Bremanger Quarry AS | Svelgen | 1998 |
| BRH Anlegg AS | Sandstad | 2012 |
| Brightskies Geoscience AS | Oslo | 2022 |
| Broichan Ltd | Inverurie Ab51 8Gl Scotland | 2023 |
| Bruland Jord Ans | Førde | 1998 |
| Brødr Gomnæs Ans | Røyse | 1995 |
| Brødremoen Sand AS | Mysen | 1994 |
| Brødremoen Sandtak AS | Røyse | 1981 |
| Brødrene Haugen Maskin Og Grus AS | Vinstra | 1974 |
| Brødrene Salamonsen AS | Lyngdal | 2005 |
| Brødrene Snortheimsmoen Ans | Røn | 1991 |
| Brønnøy Kalk AS | Velfjord | 1997 |
| Budalsgranitten AS | Budalen | 2004 |
| Bugge Naturstein AS | Eidsvåg I Romsdal | 2013 |
| Bugten Sandtak AS | Skien | 1997 |
| Bulldozer Maskinlag Produksjon AS | Sortland | 1996 |
| BW Offshore Holdings Pte.Ltd. | Sg-117440 Mapletree Business City | 2023 |
| BW Offshore Norway AS | Oslo | 2010 |
| Byron Ltd | Aberdeen Ab11 5Qp Scotland | 1998 |
| Bøeprosjekt AS | Skien | 1999 |
| Bømlo Gold Mining Company Da | Finnås | 1995 |
| C M Marine Ltd | Inverness Iv2 6Gu Scotland | 1999 |
| C Meikle Subsea Ltd | Pa5 9Ub Renfrewshire | 2018 |
| C-Deg Environmental Engineering GmbH | De-24109 Melsdorf | 2024 |
| C-Well Offshore Solutions Limited Nuf | Ab22 8Bl | 2017 |
| C10 Consulting Limited | Glasgow G3 6Ef Scotland | 2021 |
| Cabral AS | Haugesund | 2022 |
| Cactus International AS | Stavanger | 1976 |
| Cakn Holding AS | Holmestrand | 2022 |
| Caledonian Minerals AS | Ski | 2021 |
| Cameron Flow Control Technology UK Ltd Nuf | Kt13 0Ny Weybridge | 2015 |
| Canoda Offshore AB | S-754 36 Uppsala | 2002 |
| Capella Minerals Norway AS | Ski | 2019 |
| Capgemini Sverige | Oslo | 1995 |
| Cappelen Offshore Services AS | Skien | 2000 |
| Capricorn Energy PLC | Edinburgh Eh3 9By Scotland | 2020 |
| Captain Danny Wilson | Gl6 7Nr Glocestershire England | 2009 |
| Captrol AS | Randaberg | 2005 |
| Cce Engineering Services Ltd | Glasgow G75 0Ya Scotland | 2020 |
| CD Instruments Ltd | Alexandria G83 9Pn | 2025 |
| Cemas AS | Kleppestø | 2018 |
| Cemiko AS | Snarøya | 2017 |
| Chrissygibbsengineering Ltd | Aberdeen Ab21 Ojt Scotland | 2018 |
| Cimc Offshore AS | Sandnes | 2018 |
| Cinclus IV AS | Oslo | 2016 |
| CK Drift AS | Holmestrand | 2022 |
| Clariant UK Ltd | Ls184Rp Leeds | 2006 |
| Claxton Engineering Services AS | Sandnes | 2019 |
| Clean Energy Invest AS | Lysaker | 2010 |
| Clean Marine AS | Høvåg | 2026 |
| Clipper L.L.C. Nuf | Stavanger | 2021 |
| Cluaran Geoscience | Aberdeen Ab21 9Hj | 2005 |
| Cluaran Limited | Hillside By Montrose Scotland | 1997 |
| Cmo AS | Haugesund | 2011 |
| CNC Solutions 2020 Ltd | Newcastle Upon Tyne Ne16 6Dy | 2020 |
| Cnooc Petroleum Europe Limited | Uxbridge Ub8 1Lu | 2020 |
| Coflexip SA | Stabekk | 1995 |
| Cold Gold AS | Sola | 2016 |
| Compass Personnel Services UK | 77456 Katy Texas | 2009 |
| Completion Tool Company | Aberdeen Ab1 2Yg Scotland | 1996 |
| Concedo AS | Asker | 2005 |
| Connector Deepwater Solutions AS | Kokstad | 2016 |
| Connector Subsea Solutions AS | Kokstad | 2002 |
| Connector Subsea Technology AS | Kokstad | 2016 |
| Conocophillips Libya Waha Ltd | Grand Cayman, Ky1-1103 | 2023 |
| Conocophillips Norge Nuf | Tananger | 1995 |
| Conocophillips Skandinavia AS | Tananger | 1964 |
| Construction Services AS | Bergen | 1985 |
| Cosl Innovator Pte Ltd Nuf | Sandnes | 2016 |
| Cosl Norwegian AS | Sandnes | 2008 |
| Cosl Offshore Management AS | Sandnes | 2006 |
| Cosl Pioneer Pte Ltd Nuf | Sandnes | 2016 |
| Cosl Promoter Pte Ltd Nuf | Sandnes | 2016 |
| Cosl UK Limited | Aberdeen Ab44 9Eq Scotland | 2024 |
| Crisco Subsea Ltd | Aberdeen Ab15 8Fr Scotland | 2006 |
| Crystal Production AS | Oslo | 1989 |
| Cse Offshore AS | Melandsjø | 2017 |
| CSS Isotek Limited | Leeds Ls16 6Qz | 2011 |
| D. L. Caps Limited | Aberdeen Ab15 4Zn Scotland | 2015 |
| Dalan Grus AS | Øyer | 2005 |
| Dale Naturstein AS | Holmefjord | 1985 |
| Dalen Sandtak AS | Jørpeland | 2025 |
| Dalen Sortering AS | Undheim | 2006 |
| Dalset Eid AS | Nordfjordeid | 2012 |
| Damåsen Pukkverk AS | Fiskum | 2009 |
| Dansk Olie Og Naturgas AS | Dk-2970 Hørsholm | 1999 |
| David Mackenzie Subsea Services Ltd | Hs3 3Hx Isle Of Harris | 2018 |
| David Robert Love Limited | Cb7 4Pq Cambs | 2020 |
| DC Eikefet Aggregates AS | Vikanes | 1982 |
| DC Halsvik Aggregates AS | Dalsøyra | 1997 |
| DC Resources AS | Svelgen | 2002 |
| DCS Parts and Services Ltd | Wickford Ss11 8Yq | 2025 |
| De Beers Group Nuf | London Ec1N 6Ra England | 2025 |
| De Beers Marine Namibia (Pty) Ltd | Winndhoek | 2016 |
| Dea Deutsche Erdoel AG | Stavanger | 2014 |