Jonan-ku (城南区; -ku) is one of the seven wards of Fukuoka City, Japan. As of November 1, 2004, it had a population of 128,057 people, making up 9.2% of Fukuoka City, with an area of 16.02 sq. km.

Located southwest of the downtown area of Tenjin , Jonan-ku is a primarily residential area. Despite its proximity to downtown Fukuoka, Jonan-ku has suffered from a lack of transport infrastructure , leading to congested roads and difficult access to the rest of the city. This congestion should be relieved significantly when the Nanakuma Line of the Fukuoka Subway opens in 2005.

Like most of Fukuoka City, the construction in Jonan-ku is relatively recent, as the area consisted mostly of fields after World War 2, lacking even paved roads. The result has been a crowded jumble of roads, houses, apartment buildings and businesses, with no real centre to the ward. A few large parks help to create a peaceful atmosphere.

Jonan-ku is home to Fukuoka University, whose students are everpresent during the school year and help support a growing number of local convenience stores. The St-Sulpice Great Seminary of Fukuoka is another notable landmark, having been built in the 1950's and serving to train Japanese Catholic priests from Kyushu.

Historical sites include Kikuchi Shrine and Yusentei Park .