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 to Naka Ward in the total number of workplaces.

Yokohama is the second-largest city in Japan by population and by area, and the country's most populous municipality. It is the capital and most populous city in Kanagawa Prefecture, with a population of 3.7 million in 2023. It lies on Tokyo Bay, south of Tokyo, in the Kantō region of the main island of Honshu. Yokohama is also the major economic, cultural, and commercial hub of the Greater Tokyo Area along the Keihin Industrial Zone.