This article proposes a theory of the firm based on the common good. It clarifies the meaning of the term "common good" tracing its historical development. Next, an analogous sense applicable to the firm is derived from its original context in political theory. Put simply, the common good of the firm is the production of goods and services needed for flourishing, in which different members participate through work. This is linked to the political common good through subsidiarity. Lastly, implications and challenges arising from the positing of work as the common good of the firm are explored.