San'yōdō

right|thumb|300px|San'yōdō

is a Japanese geographical term. It means both an ancient division of the country and the main road running through it. The San'yōdō corresponds for the most part with the modern conception of the San'yō region. This name derives from the idea that the southern side of the central mountain chain running through Honshū was the "sunny" side, while the northern side was the "shady" (山陰 ''San'in'') side.