This study provides a new interpretation of how political authority was conceived and transmitted in the early Mongol empire (1227-59) and its successor state in Iran, the Ilkhanate (1258-1335). Authority within the Mongol empire was intimately tied to the character of its founder, Chinggis Khan, whose reign served as an idealized model for the exercise of legitimate authority amongst his political successors. After Chinggis Khans death in 1227 two distinct political traditions emerged in the Mongol Empire, the collegial and the patrimonial, each representing the political and economic interests of different social groups within the Mongol polity. These two groups formed competing ideas on how legitimate authority should be exercised in the Mongol Empire based upon Chinggis Khans legacy. The present study documents the emergence of these two streams of political authority and assesses their impact upon the constitution and character of the Early Mongol Empire and the Ilkhanate. In doing so, this book provides a more comprehensive account of how power was conceived and exercised in the Mongol Empire, particularly amongst the noyat (military aristocracy), whose contribution to the Mongol polity has traditionally received little attention.