Utility = Happiness is one philosophical view, typically called hedonism, but many philosophers disagree with it. The more general normative definition is that utility is well-being (what's good for an individual). Hedonistic utilitarians like Bentham claim that happiness is the only good thing and thus that utility is happiness. But preference utilitarians claim that the fulfillment of preferences is what's good and consider utility a measure of preference satisfaction. (Then there are debates over just what a preference is; some give a definition close to Matt Simpson's, what you would want if you were fully informed & rational.) Others have different definitions of well-being/utility.