A private island is a disconnected body of land wholly owned by a private citizen or corporation. Although this exclusivity gives the owner substantial control over the property, private islands remain under the jurisdiction of national and sometimes local governments. Their size can vary widely, from that of a typical suburban yard to several hundred square kilometers.

An island or isle is a piece of subcontinental land completely surrounded by water. Very small islands such as emergent land features on atolls can be called islets, skerries, cays or keys. An island in a river or a lake island may be called an eyot or ait, and a small island off the coast may be called a holm. Sedimentary islands in the Ganges Delta are called chars. A grouping of geographically or geologically related islands, such as the Philippines, is referred to as an archipelago.