Suō Province (周防国 Suō no kuni) was a province of Japan in the area that is today the eastern part of Yamaguchi Prefecture. It was sometimes called Bōshū (防州). Suō bordered on Aki, Iwami, and Nagato Provinces.
The ancient provincial capital was in Hōfu. Suō was ruled for much of the Muromachi period by the Ōuchi clan, who built a castle at Yamaguchi. In the Sengoku period it was conquered by the Mōri clan, and was ruled remotely by them for much of the Edo period.