Sado is a city located on Sado Island in Niigata Prefecture, Japan. Since 2004, the city has comprised the entire island, although not all of its total area is urbanized. Sado is the sixth largest island of Japan in area following the four main islands and Okinawa Island. As of July 1, 2021, the city has an estimated population of 50,610 and a population density of 59.1 persons per km². The total area is 855.69 km².