| Ocean Freight | Shipping of goods by sea using containers. |
| Ocean Waybill | A document detailing the contract for sea carriage of goods. |
| Off-hire Clause | Terms of a time charter agreement suspending payment for vessel use. |
| Off-load | Discharge of cargo from a vessel. |
| Open Rates | A rate negotiated for additional loading on a vessel. |
| Open Registry | Registry in a country offering tax or regulatory incentives to ship owners. |
| Open Top Container | A container with an open roof designed for oversized cargo. |
| Overtonnaging | Too many ships for the level of available cargoes. |
