Jōnan (城南町, Jōnan-machi) was a town located in Shimomashiki District, Kumamoto Prefecture, Japan.

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.

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 April 1, 2012, the area is part of the Minami-ku ward.

The town is the home of the Kumamoto Civil Astronomical Observatory and the namesake of asteroid 21254.

• Kumamoto City official website (in Japanese)

32°42′N 130°43′E / 32.700°N 130.717°E / 32.700; 130.717