Flag State
The country in which a ship is registered, whose laws she sails under and which is responsible for her regulatory oversight.
The flag state is the nation of a ship’s registry. It confers nationality, applies its maritime law to the vessel, issues her certificates and is responsible — under international conventions — for ensuring she meets safety, environmental and labour standards.
"Open registries" or flags of convenience let owners register in a state other than their own for cost, tax or regulatory reasons. A flag’s record on detentions and casualties is a quality signal, captured in port-state-control whitelists and greylists.
On The Maritime
Also known as: flag state, flag of convenience, ship registry.
Related terms
Port State ControlPSC
Inspection of foreign ships in national ports to verify they meet international safety and environmental standards.
Memorandum of UnderstandingMOU
A regional agreement coordinating port-state-control inspections — e.g. the Paris and Tokyo MOUs.
Classification Society
An organisation that sets technical standards for ship construction and surveys vessels against them throughout their life.
International Maritime OrganizationIMO
The United Nations agency that sets global rules for ship safety, security and pollution prevention.
Plain-English reference definition — our own explanation of a standard shipping concept, not a licensed source or legal advice. See the full glossary or the broader maritime dictionary.
Last reviewed: June 2026.