Ōshima (大島郡; -gun) is a district located in Yamaguchi, Japan.

As of 2003, the district has an estimated population of 22,070 and a density of 159.86 persons per km². The total area is 138.06 km².

Oshima is connected with Honshu by a bridge. It is one of the largest islands in the Setonaikai strait . The area is about 130 square meters. There are 230,000 people on the island. The whole island is set aside as a national park. The special product is a mandarin orange called "Oshima mikan". There are several orange groves.

There are beaches, campsites, fishing places and a hang gliding soit. Despite these things, population in the island is decreasing year after year.

The Oshima Bridge was erected in 1976. The tide is known as one of the fastest in Japan. It is the second longest span in Japan of this style of bridge. The span of the bridge is 1020m. Its color is pale green.

Katazoegahama beach is one of the more popular beaches in the west of Japan. This is also famous for camping. There is a tennis court and a roller skate rink, near the beach. Furthermore, there is a resort hotel.

SuoOshima, Yamaguchi is a sister city of Kauai, Hawaii. There is a Hawaii historical museum, which was built in 1999 in Oshima. Office workers and bus drivers in town wear colorful aloha shirts as a uniform in summer.

Towns and villages

• Kuka
• Oshima
• Tachibana
• Towa