Fukuoka, ken (prefecture), northern Kyushu, Japan. Fukuoka faces the Tsushima Strait (Eastern Channel) to the west, the Inland Sea to the northwest, the Shimonoseki Strait to the north, and the Ariake Sea to the south. Rivers draining seaward have built up extensive plains. The western coast of Fukuoka is heavily indented, and Fukuoka city, the prefectural capital, is situated on Hakata Bay, one of those indentations.