This article addresses how the anti-imperialist and the ethnic base of Korean nationalism have shaped inter-Korean relations and the relationship between both Koreas and the United States. First, the article discusses the historical process behind the formation of Korean nationalism and how nationalism has shaped North and South Korean society and politics after 1945. After reviewing how nationalism has shaped both Koreas' relations to the United States,the article ends with a discussion of the implications of the politics of nationalism for inter-Korean and U.S.-Korean relations.