Shinjuku (新宿区, Shinjuku-ku^?) is one of the 23 special wards of Tokyo, Japan. It is a major commercial and administrative centre, housing the busiest train station in the world (Shinjuku Station) and the Tokyo Metropolitan Government Building, the administration centre for the government of Tokyo.

As of 2008, the ward has an estimated population of 312,418 and a population density of 17,140 persons per km². The total area is 18.23 km².

Surrounding Shinjuku are six other wards: Chiyoda to the east; Bunkyo and Toshima to the north; Nakano to the west, and Shibuya and Minato to the south. In addition, Nerima is only a hundred meters away^{[citation needed]}. The highest point in Shinjuku is Hakoneyama (箱根山^?) in Toyama Park at 44.6 m^{[citation needed]}. The lowest point is 4.2 m near Iidabashi^{[citation needed]}.

Although the area immediately surrounding Shinjuku Station is home to hotels, department stores, specialist electronic and camera shops, cinemas, restaurants, and bars, the rest of the city is a mix of residential with commercial areas concentrated around railway stations^{[citation needed]}.