Ship registration is the process of documenting a ship's given nationality. The nationality of a ship allows it to travel internationally wherever citizens of that nation are authorized to travel. The registration is almost like the passport for the ship, itself. Per international agreements, every merchant ship must be registered to a particular country. The country to which a ship is registered is called its “flag state.” A ship is bound by the laws of its flag state, and one commonly says a ship sails “under the flag” of its country of registration