Greeeen or GRe4N BOYZ is a Japanese vocal group from Kōriyama in Fukushima Prefecture, comprising the all-male four members: HIDE, navi, 92, and SOH. On March 19, 2024, the group announced a significant change by altering their name to GRe4N BOYZ upon leaving their previous agency, High Speed Boy.

Kōriyama is a city in Fukushima Prefecture, Japan. As of 1 August 2023, the city had an estimated population of 321,938 people in 141760 households, and a population density of 425 persons per km2. The total area of the city is 757.20 square kilometers (292.36 sq mi). Kōriyama is designated as a core city and functions as a commercial center for Fukushima Prefecture. Kōriyama is the third largest conurbation in the Tōhoku region.