Usuki is a city located on the east coast of Ōita Prefecture, Japan. As of 1 October 2023, the city had an estimated population of 34,155 in 14538 households, and a population density of 120 persons per km². The total area of the city is 868.02 km2. It is famous for its Usuki Stone Buddhas, a National Treasure, and its soy sauce production.