Holbach's famous materialistic and atheistic philosophy is less known for its political dimension. Yet the author proposed an original theory of the social contract in his works of the 1770s. This article details the main features of his political thought and of his social contract, notably his proposal of an 'Ethocracy' grounded in utility and justice. This Ethocracy paves the way for a pluralist republicanism that has original features in the history of ideas. Holbach was a reader of Hobbes and Locke and an acquaintance of Rousseau, and proposed various critiques of the political writings of these authors. Through five main critiques, this article further shows the value of Holbach's positive theory on key concepts such as the state of nature, sociability, property, the general will and equality. Lastly, Holbach's potential contribution to political theory is highlighted, showing how the largely forgotten author merits our attention today.