| Orion Minerals AS | Oslo | 2025 |
| Orkla Grube AS | Fannrem | 2007 |
| Orkla Stein AS | Fannrem | 2020 |
| Orlen Upstream Norway AS | Stavanger | 2007 |
| Os Knuseverk AS | Hagavik | 1978 |
| Os Naturstein AS | Trondheim | 2015 |
| Os Tipp Og Jordsortering AS | Os | 2013 |
| Oslo Stein AS | Fornebu | 2025 |
| Otech Marine Services Norway AS | Stavanger | 2016 |
| Otillio AS | Stavanger | 2005 |
| Oz Midco AS | Stavanger | 2013 |
| P.B. Engineering (Scotland) Ltd | Gb-Hamilton Lanarkshire Ml3 6Bj | 2018 |
| P/F Pam-Offshore Service | Fo 110 Torshav | 1998 |
| Pandion Energy AS | Oslo | 2016 |
| Pandion Energy Holding AS | Oslo | 2018 |
| Panoro Energy AS | Oslo | 2018 |
| Panoro Tunisia Exploration AS | Oslo | 2010 |
| Panoro Tunisia Production AS | Oslo | 2018 |
| Paragon (Seillean) KS | Tananger | 2005 |
| Paragon Seillean AS | Tananger | 2001 |
| Parken Solutions Holding AS | Alta | 2022 |
| Paul Emmerson | Tarporley Cw6 9Hd, Cheshire | 2020 |
| Peary Spirit LLC Nuf | Stavanger | 2023 |
| Peder Erga AS | Sola | 2024 |
| Pelagia | Fr-06340 Drap | 2025 |
| Peninsula Survey Systems Ltd | Northern Irland Bt22 2Qt | 1998 |
| Perenco Vietnam AS | Oslo | 1996 |
| Perin AS | Hell | 2020 |
| Peska Holding AS | Tverrelvdalen | 2024 |
| Petoro AS | Stavanger | 2001 |
| Petrica AS | Nesbru | 2013 |
| Petrica Invest AS | Lysaker | 2018 |
| Petro Well Services AS | Ålesund | 2016 |
| Petro Well Services Limited | Ab15 8Pu Kingswell | 2016 |
| PETRO-CANADA NORWAY INC norsk avdeling av utenlandsk foretak NUF | Stavanger | 1997 |
| Petrobea Ltd | London Ec1 4Pw England | 2011 |
| Petrodata AS | Hundvåg | 2015 |
| Petrofac Facilities Management Limited | Aberdeen Ab11 5Qf Scotland | 2023 |
| Petrojarl I L.L.C. Nuf | Trondheim | 2021 |
| Petrojarl I Production AS | Trondheim | 2011 |
| Petroleum Geo-Technology AS | Trondheim | 2013 |
| Petrolia AS | Oslo | 1998 |
| Petrolia Invest AS | Oslo | 2008 |
| Petrolia Noco AS | Rådal | 2011 |
| Petrolia Rigs AS | Oslo | 1998 |
| Petrolink AS | Stavanger | 1991 |
| Petrolink Support AS | Stavanger | 1992 |
| Petromarin Holding AS | Paradis | 1996 |
| Petronor AS | Oslo | 2019 |
| Petronor Nuf | Oslo | 2015 |
| Petroplan Europe Limited | Surrey Gu1 4Uq England | 2015 |
| Petroplays Limited | Ab11 7Lh Aberdeen | 2014 |
| Phronteseas AS | Stavanger | 2020 |
| Pii Ltd | Northumberland Ne23 9Ww England | 1999 |
| Pipeline Induction Heat Ltd | Burnley Bb11 5Sw | 1995 |
| Pipeline Mechanical Services | London Wi8 2Qd England | 2018 |
| Piranema L.L.C. Nuf | Trondheim | 2021 |
| Piranema Production AS | Trondheim | 2003 |
| PKR Wynn Ltd | Doncaster Dn5 7Jh | 2018 |
| Pod-Tec Limited Nuf | Ab42 1Wn Peterhead Aberdeen Sc | 2025 |
| Polar Resources AS | Oslo | 2022 |
| Porsgrunn Pukkservice AS | Helgeroa | 1996 |
| Porthos Capital AS | Oslo | 2017 |
| Poseidon Exl 005 Ans | Lysaker | 2023 |
| Poseidon Offshore Mining AS | Oslo | 2019 |
| Poseidon Personnel Services S.A. | Ch-1618 Chatel St Denis | 2000 |
| Poseidon Subsea Ltd | Aberdeen Ab21 9Aj Scotland | 2018 |
| Pra Group Europe Portfolio AS | Oslo | 1986 |
| Premier Oil and Gas Service Ltd | Sw156P London | 2006 |
| Primary Solutions AS | Stavanger | 2020 |
| Procurement Consulting Services International Limited | Gb-Holmfirth Hd9 5Qw | 2018 |
| Prodrill Engineering Limited | Ab15 9Pe Aberdeen | 1999 |
| Proplan Project Planning AS | Tananger | 2017 |
| Proproc AS | Sandnes | 2018 |
| Prosafe Offshore Limited Nuf | Oslo | 1997 |
| Prosafe Offshore Pte Limited Nuf | Oslo | 2018 |
| Prosik AS | Bergen | 2024 |
| Przedsiebiorstwo Handlowo Uslugowe Zbigniew Marcinczak | Høvik | 2006 |
| PSW Solutions AS | Mongstad | 2012 |
| PSW Technology AS | Mongstad | 2006 |
| PTL Services | Dk-6715 Esbjerg | 2021 |
| Pukk 1 Hadeland AS | Jaren | 2012 |
| Pukk Og Gjenvinning AS | Sortland | 2024 |
| Pukkproduksjon AS | Vikersund | 1990 |
| Pure Ocean AS | Aukra | 2025 |
| PWS Crew Limited | Ab31 4Bw Aberdeenshire | 2016 |
| Pæska Skiferproduksjon AS | Alta | 2002 |
| Quad Operations Ltd | Gb-Sl6 1Bu Berkshire | 1995 |
| Quality Positioning Services BV | 3705 Lz Zeist | 1995 |
| Quartz Factory AS | Harstad | 2011 |
| R Blackett Charlton Limited | Ne6 3Pj | 1998 |
| R Madsen Holding AS | Helgeroa | 2005 |
| R Transit AS | Bergen | 2014 |
| R-T Invest AS | Kristiansand S | 2009 |
| R.B. Offshore | Northumberland Ne63 9Jw | 2023 |
| R.Nevland AS | Egersund | 2022 |
| Raingold UK Ltd | Kings Langley Wd4 8Dh England | 2011 |
| Ramco Holdings Norway AS | Florø | 2018 |
| Ramco Norway AS | Florø | 1983 |
| Ramlo Holding AS | Klæbu | 2018 |