How much of the world isn’t owned by anyone?

Approximately 43% of the Earth's surface remains unowned, though this consists almost entirely of international waters, or the "high seas," governed by maritime law for the common good. On land, the doctrine of *terra nullius*—land belonging to no one—has largely vanished, leaving only a few notable exceptions totaling less than 0.3% of the world's surface. Geography expert Mark Cooper-Jones identifies Marie Byrd Land in Antarctica as the largest unowned territory, preserved by its extreme remoteness and the 1959 Antarctic Treaty. Other instances, such as Bir Tawil between Egypt and Sudan and Gornja Siga between Croatia and Serbia, exist due to conflicting border claims where asserting ownership of one plot would mean legally forfeiting more valuable territory. While individuals like Jeremiah Heaton and Vít Jedlička have attempted to claim these lands as private kingdoms or libertarian projects, such efforts lack international recognition and often result in legal detention by neighboring sovereign states.