Koreans in Japan comprise ethnic Koreans who have permanent residency status in Japan or who have become Japanese citizens, and whose immigration to Japan originated before 1945, or who are descendants of those immigrants. They are a group distinct from South Korean nationals who have immigrated to Japan after the end of World War II and the division of Korea.

For over 15 centuries, the relationship between Japan and Korea was characterized by cultural exchanges, economic trade, political contact and military confrontations, all of which underlie their relations even today. During the ancient era, exchanges of cultures and ideas between Japan and mainland Asia were common through migration via the Korean Peninsula, and diplomatic contact and trade between the two.