Four books with one title—Empire—are the subject of this essay.Simply including the plural would have extended the list still further: see Susan E. Alcock, Terence N. D'Altroy, Kathleen D. Morrison, and Carla M. Sinopoli, eds., Empires (Cambridge: Cambridge University Press, 2001); Michael Doyle, Empires (Ithaca: Cornell University Press, 1986). I am grateful to Jane Burbank, Antonio Feros, and Molly Nolan for comments on a previous draft of this article. All were published within the past few years, and the interest they have generated reveals a widespread concern with the exercise of power on a vast scale, beyond the limits of national or continental boundaries. Yet the contemporary use of the word “empire” as a metaphor for unbounded power sits uneasily with scholarship on actual historical empires. Many historians have been trying to show that the long-term survival of empires depended on their rulers limiting their transformative ambitions even as they extended their power. The new interest in empires is nonetheless valuable because it suggests that scholars and intellectuals are emerging from their obsession with the nation-state, seen as the inevitable outcome of a movement from empire to nation, and as the political form characteristic of the “modern” era, which some scholars think is now giving way to new forms of global connections. Empire is being discovered in the past, in the present, and in the future.