It is a major commercial and administrative center, housing the northern half of the busiest railway station in the world (Shinjuku Station) as well as the Tokyo Metropolitan Government Building, the administrative center of the Tokyo Metropolitan Government.

The southern half of this area and majority of the station are in fact located in the neighboring Shibuya ward.

In 1698, Naitō-Shinjuku had developed as a new (shin) station (shuku or juku) on the Kōshū Kaidō, one of the major highways of that era.

Naitō was the family name of a daimyō whose mansion stood in the area; his land is now a public park, the Shinjuku Gyoen.

Shinjuku began to develop into its current form after the Great Kantō Earthquake in 1923, since the seismically stable area largely escaped the devastation.

Shinjuku is surrounded by Chiyoda to the east; Bunkyo and Toshima to the north; Nakano to the west, and Shibuya and Minato to the south.

[10] The current city of Shinjuku grew out of several separate towns and villages, which have retained some distinctions despite growing together as part of the Tokyo metropolis.

Many companies have their headquarters or Tokyo offices in this area, including regional telephone operator NTT East, global camera and medical device manufacturer Olympus Corporation, electronics giant Seiko Epson,[13] video game developer Square Enix,[14] fast food chains McDonald's Japan and Yoshinoya,[15] travel agency H.I.S.,[16] Subaru Corporation (Subaru),[17] railway operator Odakyu Electric Railway, construction giants Taisei Corporation[18] and Kumagai Gumi,[19] medical equipment manufacturer Nihon Kohden,[20] Enoki Films,[21] navigation software company Jorudan,[22] instant noodle giant Nissin Foods,[23] automotive components manufacturer Keihin Corporation,[24] and regional airline Airtransse.

The Geographical Survey Institute (Kokudo Chiriin) names Tōkyō (the city) as capital of Tōkyō-to (the prefecture/"Metropolis").

A list of railway lines passing through and stations located within Shinjuku includes: Shuto Expressway: National highways: Other major routes: Moved: Public high schools are operated by the Tokyo Metropolitan Government Board of Education.