 | Ny-Hus AS | 931120875 | BERGEN |
| NYLAND BYGGEADMINISTRASJON AS | 934767403 | SANDNES |
| NYMOE ELEKTRO AS | 986673768 | ALTA |
| NYPAN HAGE & ANLEGG AS | 985264392 | TRONDHEIM |
| NYRØ TEKNOLOGI AS | 924403152 | HEIM |
| NYSTED AS | 976074580 | BALSFJORD |
| NYSTØL & FAGERHOL AS | 981463579 | VANYLVEN |
| NY STRUKTUR AS | 918294112 | OSLO |
| NYTTBYGG AS | 913359771 | SARPSBORG |
| NYTTIGE NEVER - TRØNDELAG AS | 915011322 | TRONDHEIM |
| NYTT PROSJEKT AS | 974389657 | OSLO |
| NYVOLD INSTALLASJON AS | 957724787 | OPPDAL |
| NYVOLL CONSULT AS | 993172537 | NITTEDAL |
| NZ RØRSERVICE AS | 922129800 | LILLESTRØM |
| Ø.ANTONSEN AS | 964377111 | BERGEN |
| O A SANNE AS | 932521806 | MOLDE |
| OBAS VEST AS | 960018095 | DRAMMEN |
| OBB AS | 921230125 | BJØRNAFJORDEN |
| OB BRENDEMOEN AS | 965678492 | NORD-FRON |
| ØBE AS | 921863993 | BÆRUM |
| OBERRAUTER BYGG OG SPRENGNING AS | 915540813 | VESTBY |
| OBOS PROSJEKT AS | 931536532 | OSLO |
| OBRON AS | 999536492 | AURE |
| OBRON ØST AS | 998667852 | STANGE |
| ØB RØR AS | 936606040 | ØRSTA |
| ØB-TAK AS | 971072830 | OSLO |
| O.B. Wiik A/S | 934122224 | LILLESTRØM |
| OCAB AS | 916326211 | BÆRUM |
| ODAL ANLEGGSDRIFT AS | 932475057 | NORD-ODAL |
| ODAL BYGG AS | 931933795 | SØR-ODAL |
| ODAL ENTREPRENØR AS | 994449826 | SØR-ODAL |
| O D BYGG AS | 924661399 | HØYANGER |
| ODD ARNE AARSTAD | 977105579 | KONGSVINGER |
| ODD BARTHO-HANSEN & SØNNER AS | 955499697 | FÆRDER |
| ODD BJERKEVOLL AS | 942654723 | VESTNES |
| ODD EINAR KNE AS | 974904535 | STEINKJER |
| ODD ERLING LØVØY | 968174835 | HERØY (MØRE OG ROMSDAL) |
| ODD FARMEN AS | 925415693 | LARVIK |
| ODD HAGERUD AS | 976018192 | EIDSKOG |
| ODD HANSEN AS | 971090715 | HAUGESUND |
| ODDMUND GROVEN AS | 923627804 | ØRLAND |
| Odd-Petter Hosen AS | 947714821 | ÅFJORD |
| ODD SMÅGE AS | 954505170 | AUKRA |
| ODD STENSVOLD AS | 995680084 | LARVIK |
| ODDVAR MELING AS | 980151794 | STAVANGER |
| ODDVAR NYBROT AUTORISERT RØRLEGGERFIRMA | 930232882 | BJØRNAFJORDEN |
| ODDVAR ØYGARD AS | 985793581 | ÅL |
| ØDEGAARD ANLEGG AS | 992170905 | BRØNNØY |
| ØDEGAARD OG STERTEN AS | 997907116 | BÆRUM |
| ØDEGÅRD BYGG OG MASKIN AS | 919232773 | LUSTER |