Sōsa (匝瑳市, Sōsa-shi) is a city located in Chiba Prefecture, Japan.

The northern section, a mixture of valleys, ports and rice fields, consists of a plateau made up of complicated terrain and features.

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

Sōsa has a mayor-council form of government with a directly elected mayor and a unicameral city council of 18 members.

In terms of national politics, the city is part of Chiba 10th district of the lower house of the Diet of Japan.