Kikaijima (Japanese: 喜界島; Amami: Kyaa; Okinawan: Cikai-zima) is one of the Satsunan Islands, classed with the Amami archipelago between Kyūshū and Okinawa.

The island, 56.93 square kilometres (21.98 sq mi) in area, has a population of approximately 7,657 people. Administratively the island forms the town of Kikai, Kagoshima Prefecture. Much of the island is within the borders of the Amami Guntō Quasi-National Park.

The name Kikai is attested in Old and Middle Okinawan with the various phonemic kana spellings ききや, きゝや, きちゃ, きちや, ちちや, and ちちやァ, which may have been the antecedent of the Kikai name.

Kikaijima is isolated from the other Amami islands, and is located approximately 25 kilometres (13 nmi; 16 mi) east of Amami Ōshima and approximately 380 kilometres (210 nmi; 240 mi) south of the southern tip of Kyūshū. It is the easternmost island in the Amami chain. Compared with Amami Ōshima and Tokunoshima, Kikaijima is a relatively flat island, with its highest point at 214 metres (702 ft) above sea level. It is a raised coral island with limestone cliffs, and draws the attention of geologists as it is one of the fastest rising coral islands in the world.

The climate of Kikaijima is classified as a humid subtropical climate (Köppen climate classification Cfa) with very warm summers and mild winters. The rainy season lasts from May through September. The island is subject to frequent typhoons.

Due to its relative isolation, Kikaijima is home to several rare species endemic to the island itself, or more generally to the Ryukyu archipelago. However, it is one of the few islands in the Amami chain to which the venomous habu viper is not indigenous. Larger biogenically coated nodules (25–130 mm in diameter), named macroids, have been found off Kikai-jima shelf, at water depths of 61 to 105 m. These macroids are made up by encrusting acervulind foraminifera. These macroids host boring bivalves whose holes represent the ichnogenus Gastrochaenolites.

Although the Ryukyu Islands appeared in written history as Japan's southern frontier, the name of Kikaijima was not recorded in early years. The Nihongi ryaku (c. 11th–12th centuries) states that in 998 Dazaifu, the administrative center of Kyūshū ordered Kikajima (貴駕島) to arrest the Nanban (southern barbarians), who in the previous year had pillaged a wide area of western Kyūshū. The Nanban were identified as Amami islanders by the Shōyūki (982–1032 for the extant portion). Accordingly, it is assumed that Dazaifu had a stronghold in the Kikaijima concerned.

The Shinsarugakuki, a fiction written by an aristocrat Fujiwara no Akihira in the mid-11th century, introduced a merchant named Hachirō-mauto, who traveled all the way to the land of the Fushū in the east and to Kika-no-shima (貴賀之島) in the west.