Jōnan (城南町 Jōnan-machi) was a town located in Shimomashiki District, Kumamoto, Japan.
On March 23, 2010 Jōnan, along with the town of Ueki, from Kamoto District, was merged into the expanded city of Kumamoto and no longer exists as an independent municipality.[1]
As of 2003, the town had an estimated population of 19,885 and the density of 539.18 persons per km². The total area was 36.88 km².
The town is the home of the Kumamoto Civil Astronomical Observatory and the namesake of asteroid 21254.