A growing number of scholars, commentators, and pundits describe the contemporary US as an empire. This article argues that these authors have not paid sufficient attention to the historiography of empire and imperialism. Indeed, the historiography of the British and American empires offers important lessons for current debates including what is the appropriate definition of the American empire, what are the social and political foundations of the American Empire, and what are the consequences of the American Empire for the US and the wider world.