This paper articulates an Aristotelian theory of professional virtue and provides an application of that theory to the subject of engineering ethics. The leading idea is that Aristotle's analysis of the definitive function of human beings, and of the virtues humans require to fulfill that function, can serve as a model for an analysis of the definitive function or social role of a profession and thus of the virtues professionals must exhibit to fulfill that role. Special attention is given to a virtue of professional self-awareness, an analogue to Aristotle's phronesis or practical wisdom. In the course of laying out my account I argue that the virtuous professional is the successful professional, just as the virtuous life is the happy life for Aristotle. I close by suggesting that a virtue ethics approach toward professional ethics can enrich the pedagogy of professional ethics courses and help foster a sense of pride and responsibility in young professionals.