Suō-Ōshima (周防大島町, Suō-Ōshima-chō) is a town and an island located in Ōshima District, Yamaguchi Prefecture, Japan.

Suo-Oshima has established a sister island relationship with the County of Kauai, Hawaii in 1963.

Current Mayors Takumi Shiiki (Suo-Oshima) and Bernard P. Carvalho, Jr. (Kauai) signed a Reaffirmation of Friendship agreement.

The average annual rainfall is 1,736.1 mm (68.35 in) with June as the wettest month.

[2] Per Japanese census data, the population of Suō-Ōshima in 2020 is 14,798 people.