Sasebo is a core city located in Nagasaki Prefecture, Japan. It is the second-largest city in Nagasaki Prefecture, after its capital, Nagasaki. As of 1 April 2024, the city had an estimated population of 230,873 in 102,670 households, and a population density of 540 persons per km2. The total area of the city is 426.01 km2 (164.48 sq mi).