The present chapter investigates the use of the expression bonum commune in two political works by William of Ockham: the third part of the Dialogus and the Octo quaestiones de potestate papae. The choice of these works is motivated by the fact that they represent the final – and most mature – phase of the English Franciscan’s political reflection. Relying on the findings of previous scholarship, the author believes it is appropriate to focus on the use of the expression rather than on a determination of its meaning, which seems to be taken for granted by Ockham. The contribution highlights three main uses of the expression: (1) as a criterion for distinguishing, along the lines of Aristotle’s Politics, between upright and deviant constitutional forms; (2) as a limit to the exercise of power by a legitimate power; and (3) as “a conceptual device” that aims to relativise the conclusions of political theory (e.g., the identification of the best constitutional form), motivated by Ockham’s awareness of the intrinsic contingency and mutability of historical events. Indeed, safeguarding the common good in certain situations, according to the English Franciscan, may require a solution that deviates from the ideal paradigm. In the course of the analysis, it appears that Ockham, despite his reputation as an individualist philosopher, consistently applies the principle of the subordination of the individual good to the common good.