Shiroishi (白石町, Shiroishi-chō) is a town located in south-central Saga Prefecture, Japan, in Kishima District.

The total area of the town is 99.56 km2 (38.44 sq mi) Located in the Saga plains, Shiroishi is bordered by the Ariake Sea to the southeast.

The port of Suminoe Bay, in the mouth of the Rokkaku River, has the largest tidal range in Japan with a maximum of about 6m at spring tide.

Saga Prefecture Shiroishi has a humid subtropical climate (Köppen Cfa) characterized by warm summers and cool winters with light to no snowfall.

The villages of Hashishita, Fukudomi, Fukuji, Kinkō, Kita-Ariake, Minami-Ariake, Rokkaku, Ryūō, and Suko were established on April 1, 1889 with the creation of the modern municipalities system.