尼库瑙岛是太平洋岛国基里巴斯的环礁，属于吉尔伯特群岛的一部分，长14.2公里、宽2.5公里，面积18.2平方公里，岛上有数个湖泊，2005年人口约1,912。

Nikunau is a low coral island in the Gilbert Islands and forms a council district of the Republic of Kiribati. It consists of two parts, (the larger one in the northwest), joined by an isthmus about 150 metres (490 ft) wide.

There are several landlocked, hypersaline lagoons located within the island, measuring about 30 hectares (74 acres) in area. The island is surrounded by a narrow fringing reef. Vegetation on Nikunau is moderately dense and consists largely of coconut palms and pandanus.