Firma O - Mandal
- Ossia AS
- Orissa AS
- Opk AS
- Opk AS
- Ovata AS
- Oriental Market AS
- Omestad Bygg AS
- Osk Invest AS
- Olav Kristensen
- Otterdal Yoga
- Ove Aanestad
- Oftenes Eiendom AS
- Oluf Lohne AS
- Oeg Holding AS
- Olivias Hus
- Oluf Lohne
- Os Studentbedrift
- Of Capital AS
- Oakland Norge AS
- Odd Hallingsgård
- Omland Invest AS
- Ocean II AS
- Ocean Equity AS
- Osb Anlegg AS
- Orelunden Dagsenter
- Olka Invest AS
- Oddvar Løge
- Omland Bygdelag
- Oskar Kaaløy AS
- Omlandsneset Vel
- Oas Vaktmesterservice AS
- Omre Næringspark AS
- Olsen Roald
- Omland Bygdelag
- Olsen Knut
- O. Edland AS
- Oddvar Haaland
- Olivia Capital AS
- Oei Holding AS
- Oksana Vyhovska
- Ogsy Norge
- Og Tjenester Vakthold
- Odd Albert Wrålsen
- Oasen skole Mandal AS
- Otera Infra AS Avd Mandal
- Oddmund Hennestad Døble
- Odd Christian Hagen
- Odd Ørnulf Stray
- Oksevollen 23-25
- Odd Harket Steindal
- Orlando Gutiérrez Suarez
- Olje & Utstyr A/S
- Oksevollen 23-25
- Opplæringskontor for Byggfag
- Ole Bent Røiseland
- Ole Guttorm Ihme
- Ole Kristian Eigebrekk
- Oakland Møbler Ålesund AS
- Oakland Møbler Stavanger AS
- Oakland Møbler Trondheim AS
- Ove Rolf Torland
- Otto Svein Kragh
- Oakland Møbler Bergen AS
- Odd Magne Ljosland
- Orn Industri og Bygg AS
- Overskuddsfabrikken Kjersti Tveit Nilsen
- Olsen Stein og Betong AS
- Ophaug Eiendom & Invest AS
- Oas Bil og Båtservice AS
- O.A.N Holding AS
- Ollis Candyworld V/Nadja Omdal
- Ole Georg Hjorteland - H.Bygg
- Omdal Consult V/Stacy Feyling Omdal
- Opplæringskontoret for Byggfag i Mandal