Hainan is an island province of the People's Republic of China (PRC), consisting of the eponymous Hainan Island and various smaller islands in the South China Sea under the province's administration. It is the southernmost province of China, and the name means "south of the sea", reflecting the island's position south of the Qiongzhou Strait, which separates it from Leizhou Peninsula of the Chinese mainland.

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.