Minamidaitōjima (南大東島), also spelt as Minami Daitō or Minami-Daitō, is the largest island in the Daitō Islands group southeast of Okinawa, Japan. It is administered as part of the village of Minamidaitō, Okinawa. Shimajiri District, Okinawa.. The island is entirely cultivated for agriculture, although it lacks freshwater sources. The island has no beaches or harbor, and cargo must be loaded/offloaded by crane; however the island has an airport Minami Daito Airport ( airport code "KTD").

It is uncertain when Minamidaitōjima was first discovered. It is possible that it was discovered by the Spanish in 1587, when Pedro de Unamuno named it and Kitadaitōjima as the "Islas sin Probecho". In 1788 the British captain John Meares named an island in the vicinity “Grampus Island”, but the recorded coordinates are not correct and it is not certain which of the Daitō island he sighted. The French also reported sighting an island in 1807. However, on 2 July 1820 the Russian vessel Borodino surveyed the two Daitō islands, and named the south as "South Borodino Island".

The island remained uninhabited until formally claimed by the Empire of Japan in 1885. In 1900, a team of pioneers from Hachijōjima, one of the Izu Islands located 287 kilometres (178 mi) south of Tokyo led by Tamaoki Han'emon (1838 – 1910), became the first human inhabitants of the island, and started the cultivation of sugar cane. The population reached 4000 in 1919. During this period until World War II, Minamidaitōjima was owned in its entirety by Dai Nippon Sugar (now Dai Nippon Meiji Sugar), which provided community services and subsidized pricing for its employees, and of whom were seasonal workers from Okinawa and Taiwan.

The island was garrisoned by the Japanese military in 1942. As the war situation worsened for Japan, many of the civilian inhabitants were evacuated to Okinawa, Kyushu or Hachijojima in 1944. The island was repeatedly bombed and shelled by the United States Navy from February to June 1945.

After World War II, the island was occupied by the United States, at which time its civilian population was 1426. The island was returned to Japan in 1972.

Minamidaitōjima is a relatively isolated coralline island, located approximately 9 kilometres (4.9 nmi) south of Kitadaitōjima, the second largest island of the archipelago, and 360 kilometres (190 nmi) from Naha, Okinawa. As with the other islands in the archipelago, Minamidaitōjima is an uplifted coral atoll with a steep coastal cliff of limestone (the former fringing coral reef of the island), and a depressed center (the former lagoon of the island). The island is roughly oval in shape, with a circumference of about 13.52 kilometres (8.40 mi), length of 4.85 kilometres (3.01 mi) and an area of 11.94 square kilometres (4.61 sq mi). The highest point is 74 metres (243 ft) above sea level.

The 660 (as of June 1, 2013) inhabitants live in a village in the center of the island.

Minamidaitōjima has a humid subtropical climate (Köppen climate classification Cfa) with very warm summers and mild winters. Precipitation is significant throughout the year; the wettest month is June and the driest month is February. The island is subject to frequent typhoons.