Defining corruption as the exercise of public power for private, selfish ends, many theorists have argued that individuals can be corrupt even if their actions are legal. This essay explores the knotty question of when legal corporate action is corrupt. It argues that when corporations exercise public power, either through monopolistic control of a market or through campaign contributions and support of governmental actors, they are subject to the same responsibilities of anyone who exercises public power. Therefore, as a theoretical matter, we should call corporations corrupt when they exercise public power selfishly, in a way that puts their own interests over the public's interests. Because they make legal corporate corruption less likely, global anticorruption campaigns should therefore emphasize antimonopoly laws and campaign finance laws.