Shinjuku, officially called Shinjuku City, is a special ward in the Tokyo Metropolis in Japan. It is a major commercial and administrative center, housing the northern half of the busiest railway station in the world and the Tokyo Metropolitan Government Building, the administration center for the government of Tokyo. As of 2018, the ward has an estimated population of 346,235 and a population density of 18,232 people per km2. The total area is 18.23 km2.