was a coastal town located at the mouth of the Kozagawa river in Higashimuro District, Wakayama Prefecture, Japan.
In 2003, the town had an estimated population of 5,587 and a density of 121.43 persons per km2. The total area was 46.01 km2.
On April 1, 2005, Koza was merged into the expanded town of Kushimoto (formerly from Nishimuro District, now within Higashimuro District).