San'yō (山陽町 San'yō-chō) was a town located in Akaiwa District, Okayama, Japan.
On March 7, 2005 San'yō was merged with the towns of Akasaka, Kumayama and Yoshii, all from Akaiwa District, to form the new city of Akaiwa.
As of 2003, the town had an estimated population of 24,939 and a density of 719.95 persons per km². The total area was 34.64 km².