Armed forces around the world are rapidly developing uncrewed maritime vehicles (‘UMVs’) for use in military operations. Key to the strategic value of UMVs is that they will have no people on board and instead be remotely controlled or, in the future, be capable of carrying out some or all of their mission autonomously. But will they fit into the existing categories of the law of the sea set out in the United Nations Convention on the Law of the Sea (‘UNCLOS’)? This article considers whether two of the basic classifications of this body of law — being categorised as a ‘ship’ or ‘vessel’ and being a ‘warship’ — require people to be on board the vehicle and thus exclude UMVs. These categories are critical for the distribution of rights and obligations in UNCLOS. Failing to qualify as a ship would significantly limit the strategic value of UMVs, restricting their navigational rights and possibly preventing states from claiming sovereign immunity.