A Neutral territory is a territory (not a sovereign state) that is not an integral part of any state (neither independent, nor dependent on a single state, nor colonized or under protectorate, nor a concession), and yet is not terra nullius, but is the object of an agreement under international law between at least two parties (usually bordering states and/or their colonisators etcetera) that neither shall establish, at least for the duration of the agreement's validity, effective control over it.
When it is a delimited zone bordering at least one of the partners, the term neutral zone applies. This had been the case for:
in the colonial era, the neutral zone between Thailand and French Indochina, 25 kilometres wide (roughly 15.5 miles) on the right bank of the Mekong, was placed under French control but formally remained under Thai sovereignty
