This paper provides a theory of a monopolist in general equilibrium. We assume that the firm's decisions are based on the preferences of shareholders and/or other stakeholders. We show that the monopolist will charge less than the profit-maximising price, since shareholders suffer part of the cost of a price rise if they are also consumers. If price discrimination is possible, the resulting equilibrium will be Pareto efficient. We use the model to examine the effects of increasing stakeholder representation in firms. A related result shows that a non-profit firm will produce fewer negative externalities.