San'yōdō (山陽道) is a Japanese term for both an ancient division of the country and the main road running through the region.
San'yōdō was one of the main circuits of the Gokishichidō system. It was first established during the Asuka period. Over centuries, the government functions of the Gokishichido became less important. However, the traditional eight regions, including San'yōdō, remained cultural markers.