The flag of Gibraltar is an elongated banner of arms based on the coat of arms of Gibraltar, granted by Royal Warrant from Queen Isabella I of Castile on 10 July 1502. The flag of Gibraltar is unique as it is the only British Overseas Territory which does not feature the Union Jack in any form, although the latter is widely flown as a standalone flag within the territory.

The coat of arms of Gibraltar was first granted by a Royal Warrant passed in Toledo on 10 July 1502 by Isabella I of Castile during Gibraltar's Spanish period. The arms consists of an escutcheon and features a three-towered red castle under which hangs a golden key.