Kainan, city, northwestern Wakayama ken (prefecture), west-central Honshu, Japan. It lies on Wakanoura Bay and borders Wakayama city to the north.
Kainan was formed in 1934 through the merger of the towns of Kuroe, Hiigata, and Uchiumi. The city has been known since the Edo (Tokugawa) period (1603–1867) for its Kishu (Kuroe-nuri) lacquerware and for the production of Japanese umbrellas. Kainan’s modern industry includes petrochemical plants developed on reclaimed parts of the coast. Pop. (2010) 54,783; (2015) 51,860.