The 23 special wards of Tokyo are a unique form of municipality under Japan's 1947 Local Autonomy Law. They are city-level wards: primary subdivisions of a prefecture with municipal autonomy. Together, they cover 627 km2 (242 sq mi) and, as of 2024, house roughly 9.8 million residents, yielding a density of about 15,742 people/km2. Similar ward systems are legally possible in other prefectures, but none have been established.