We have so far registered 4,509 shipyards
| Name | | Omastrand Kleven Verft A/S, Ulsteinvik |
| O.M. Olsens, Bratteklev, Arendal |
| Onomichi Zosen K.K., Onomichi, Japan |
| Onsøy, Fredrikstad |
| O. Olsen, Kristiansand |
| O. Pedersen, Buer, Sandefjord |
| Open JSC ,Astrakahn |
| O. Pittfield, Courtney Bay, St.John, New Brunswick, Canada |
| O.P. Knudsens Verft, Kokkenes, Lillesand |
| O. & P. Knudsens verft, Lillesand |
| O. & P. Knudsens Vestre Verft, Lillesand |
| O.P. Moe & Søn, Kristiansand |
| Opsanger, Kvinnherad |
| Oregon Ship Building Co., Portland, OR, USA |
| Oregon Ship Building Corp., Wilmington |
| O. Reinertsens Verft, Lillesand |
| Orenstein & Koppel, Lübeck, Tyskland |
| Orenstein Koppel und Lübecker Maschinenbau A/G, Lübeck, Tyskland |
| Orlogsværftet, København, Danmark |
| Ormestads Slip & Baadbyggeri, Fjeldvik |
| Ortnevik Båtbyggeri L/L, Ortnevik,Sogn |
| Osaka Iron Works Ltd. Innoshima, Japan |
| Osaka Iron Works. Ltd., Osaka, Japan |
| Osaka Zosensho, Osaka, Japan |
| Osbourne, Graham & Co. Ltd., Sunderland, UK |
