The Ryukyu Islands (琉球諸島, Ryūkyū-shotō^?), known in Japanese as the Nansei Islands (南西諸島, Nansei-shotō^?, lit. "Southwest Islands") and also known as the Ryukyu Arc (琉球弧, Ryūkyū-ko^?), are a chain of Japanese islands that stretch southwest from Kyushu to Taiwan: the Ōsumi, Tokara, Amami, Okinawa, and Sakishima (Miyako and Yaeyama) islands, with Yonaguni the southernmost. The largest of the islands is Okinawa.

The islands have a subtropical climate with mild winters and hot summers. Precipitation is very high, and is affected by the rainy season and typhoons. Except the outlying Daitō Islands, the island chain has two major geologic boundaries, the Tokara Strait between the Tokara and Amami Islands, and the Kerama Gap between the Okinawa and Miyako Islands, dividing the islands into the Northern, Central, and Southern Ryukyus.

The northern Ryukyus fall under the cultural sphere of Kyūshū; the people are ethnically Japanese and speak the Osumi (Kagoshima) dialect of Japanese. The central and southern islands are characterized by coral reefs. The native population are collectively called Ryukyuans, and show a great degree of internal diversity. They speak the Ryukyuan languages, which are native to each island and distinct from one another. The outlying Daitō Islands were uninhabited until the Meiji period, when their development was started mainly by people from the Izu Islands south of Tokyo, and speak a Hachijo dialect.