Maritime flag

A flag flown by a vessel or used at sea to identify nationality, ownership, status, or intent, or to communicate signals.

Ensign: A flag displayed by a vessel to indicate its nationality or institutional affiliation. A vessel's ensign is its principal national identification flag.
Flag state: The state whose flag a vessel is entitled to fly and whose laws govern it on the high seas. A ship's flag identifies the state responsible for regulating it.
Naval ensign: A flag flown by a naval vessel to identify its navy or country. Naval ensigns developed as formal identifiers for warships.
Pirate flag: A flag associated with pirates, often used to threaten or identify a pirate vessel. Pirate flags declared a hostile identity rather than lawful national allegiance.
Courtesy flag: A flag flown by a visiting vessel to acknowledge the jurisdiction of the country it has entered. Foreign vessels commonly display the host country's flag as a courtesy.
Ship registration: The process by which a vessel is recorded under a state's laws and authorized to fly its flag. Registration establishes the legal basis for a vessel's national flag.
British Red Ensign: The British maritime flag historically associated with merchant shipping and now used as the United Kingdom's civil ensign. It exemplifies the development of a national flag specifically for merchant vessels.
False flag operation: An act designed to conceal its true sponsor by attributing it to another party. A vessel may misuse a flag to disguise its identity or allegiance.
International Code of Signals: A standardized system for communicating messages between ships using flags, radio, and other means. Its flag alphabet turns hoisted combinations into navigational and safety messages.
Flag protocol: Rules and customs governing the display, precedence, and handling of flags. Protocol determines where maritime flags are hoisted and how they are treated.

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FlagBroader topic: At sea, flags identify ships and communicate information across distance.