The damaging effects of the activities of corporations on the natural environment have given rise to the need to evaluate corporate policies, decisions, and actions affecting the natural environment on moral grounds. There are two important questions that need to be addressed in this regard. The first is whether corporations have a moral obligation to protect the natural environment, which is over and above their economic duty to maximize profits for their stockholders and their legal duty to obey environmental laws. And the second is, given that they do have this moral obligation, what sort of environmental ethical theory (homocentrism, biocentrism, utilitarianism) ought to guide the exercise of such an obligation? This paper argues that corporations do have such moral obligations, for they are moral agents in virtue of their nonmetaphorical possession of rational capacities. This, however, implies that the corporations’ exercise of this obligation can only be properly guided by a rationalist type of ethics.