The largest city on the island by population is Fukuoka, Fukuoka, populated approximately 1.4 million people – a major business center with a major international airport as well as one of five stock exchanges in Japan. Kitakyushu, Fukuoka is also a designated city and major center for heavy industries, populated slightly less than a million. Kumamoto and Kagoshima are 3rd and 4th biggest, populated more than a half million. Nagasaki has one of the oldest international ports, which had been the only gateway to the foreign countries during the Edo Period, from mid 16th to mid 18th centuries.

For more information, please see wikipedia or the Japan-Guide.com.