is a city located on Sado Island (佐渡島 or 佐渡ヶ島, both Sadogashima) in Niigata Prefecture, in the Chūbu region of Japan. Since 2004, the city has comprised the entire island, although not all of its total area of is urbanized. Sado is the sixth largest island of Japan in area following the four main islands and Okinawa Island (excluding the Northern Territories).