Sinjai Regency is a regency located in the South Sulawesi province of Indonesia. It covers a total area of 819.96 km2 and is geographically separated from the Bone Regency to its north by the River Tangka. The administrative region includes the Nine Islands, an archipelago situated in the Gulf of Bone off the east coast of the southern peninsula of Sulawesi.
The principal town of the regency is Sinjai, which serves as a port on the east coast of the southern peninsula. According to census data, the population grew from 228,936 in 2010 to 259,478 in 2020, with an estimated population of 278,527 as of mid-2025.