Kasaoka is a city situated in the Okayama Prefecture of Japan. As of March 1, 2023, the city maintains an estimated population of 45,404 residents living across 21,987 households. It covers a total land area of 136.24 square kilometres, resulting in a population density of approximately 330 inhabitants per square kilometre.
The municipal district of Kasaoka is notable for its geography within the Seto Inland Sea. It includes 31 outlying islands, which feature seven inhabited islands located specifically within the Kasaoka Islands archipelago.