Sasebo (佐世保市; -shi) is a city located in Nagasaki, Japan.
As of 2003, the city has an estimated population of 240,300 and the density of 967.70 persons per km². The total area is 248.32 km².
Sasebo is a base of the United States Navy, as well as Japan's Maritime SDF.
The city was founded on April 1, 1902.