Yokosuka is a city in Kanagawa Prefecture, Japan. As of October 2017, the city has a population of 409,478, and a population density of 4,066 inhabitants per square kilometre. The total area is 100.7 km2. Yokosuka is the 11th most populous city in the Greater Tokyo Area, and the 12th in the Kantō region. The city is host to United States Fleet Activities Yokosuka.