The LOSC provides for a State to fix the conditions for the grant of its nationality to ships, for the registration of ships in that State’s territory, and for the right to fly its flag. The State is also required to issue ships to which it has granted the right to fly its flag, documents to that effect (LOSC Article 91). The historical derivation of “tunnage” and ship registration is recalled as is the development of the customary law of registration of ships, through national and international legislation, from a restrictive device to one that allows unrestricted global freedom of choice of flag State. The lack of any prescriptive requirement in maritime regulations for registration of ships, and the failed attempt to codify registration of ships through an international instrument is identified and analysed. Issues associated with widespread non-observance of the requirement under the LOSC for a ship to be surveyed before registration to ensure that it is seaworthy are identified and analysed. Dual nationality, and transfer of registration , are discussed in the context of the requirements of the LOSC and the practicalities of everyday operation of ships.