Even if political theorists rarely read him, Italian political thinker, Marsilius of Padua, presents one of the most radical theories of the multitude prior to Machiavelli and Spinoza. This article reconstructs Marsilius of Padua's political theory of the multitude in his Defender of Peace and pays special attention to two main sources from which Marsilius frames his theory: Aristotle and Ibn Rushd. Compared to Aristotle, Marsilius advances a more epistemic view of the multitude as a lawmaker. Marsilius’ ideas on the multitude also depend on Ibn Rushd's theory of collective knowledge and, to a certain extent, on his position on natural law.