Kōhoku-ku (港北区) is one of the 18 wards of the city of Yokohama in Kanagawa Prefecture, Japan. As of March 1, 2012, the ward had an estimated population of 332,488, with 156,198 households and a population density of 10,588.79 persons per km². The total area was 31.40 km². Kōhoku Ward has the largest population of Yokohama's 18 wards, and ranks second only to Naka Ward in the total number of workplaces (1996 Workplace and Corporate Statistics Survey). Kōhoku Ward is located in eastern Kanagawa Prefecture, and on the northeastern borders of the city of Yokohama.
The area around present-day Kōhoku Ward was formerly part of Tsuzuki District in Musashi Province. During the Edo period, it was a rural region classified as tenryō territory controlled directly by the Tokugawa shogunate, but administered through various hatamoto. After the Meiji Restoration, the area became part of the new Kanagawa Prefecture in 1868. In the cadastral reform of April 1, 1889, the area was divided into numerous villages. In April 1939, it was annexed by the neighboring city of Yokohama. Kōhoku Ward is largely a regional commercial center and bedroom community for central Yokohama, Kawasaki and Tokyo.