The Mongol Empire changed the world, but early chronicles of its conquests, written from regional perspectives and widely dispersed, could not convey its far-reaching significance. The Khan and the Unicorn details how historians from different cultures collectively rediscovered their common past and transformed the scattered records of Chinggis Khan’s conquests into world history. Between the seventeenth and nineteenth centuries, as new empires competed for control of Eurasian lands once ruled by the Mongols, historians encountered a wealth of unfamiliar materials previously unknown to them. Aided by methodological innovations, they created more coherent and multifaceted accounts of Mongol power. Drawing on sources in Chinese, Manchu, Mongolian, and European languages, Matthew Mosca tracks this process of rediscovery from the vantage of Beijing. The Qing court led the transformation by assigning multilingual staff to integrate historical information into pioneering studies. Mosca reconstructs the emergence of a knowledge circuit linking Beijing to other scholarly centers, notably Paris, St. Petersburg, and Tokyo. As conflicting appraisals of the Mongol Empire came into contact, debates flared over how to interpret the collision of nomadic and sedentary societies, often cast as a clash between civilization and barbarism. Whether valorized or villainized, Mongol imperial power came to be recognized as a driving force in world history.