| Native Name: | 沖縄社会大衆党 Okinawa Shakai Taishū-tō |
| Chairman: | Tetsumi Takara |
| Founded: | 31 October 1950 |
| Headquarters: | Naha, Okinawa |
| Ideology: | Social democracy |
| Position: | Left-wing[1] |
| Colors: | Green |
| Seats1 Title: | Representatives |
| Seats2 Title: | Councillors |
| Seats3 Title: | Okinawa Assembly |
| Country: | Japan |
is a local political party in Okinawa, Japan. The party's name is abbreviated as or . The party primarily adheres to social democracy.
The party was founded on 31 October 1950 during the US occupation of the region. On 29 April 1952, the party launched an Association for Promotion of Reversion to Japan, which initiated a signature campaign for the demand of reunification with Japan. The campaign gathered more than 199,000 signatures (72%+ of the eligible voters of Okinawa).[2] At the time, such a campaign was initiated by liberals/leftists, including Okinawa Social Mass Party and another local party called .
After Okinawa's restoration to Japan in 1972, the latter party was merged into Japanese Communist Party. Okinawa Social Mass Party, on the other hand, did not join any mainland Japanese parties, and continues as a local party to this day.
The party has been influential as the leading left-of-centre party in the prefecture.