Scholars agree that Aristotle held a view that has been called "Aristotelian Essentialism" , but disagree about what this thesis entails. I reconstruct as the view that there are certain individuals, namely substances, that have essences, and that essences are to be understood as "explanatorily basic" features of an individual--features of an individual substance that serve as part of a scientific explanation of the presence of other features of that individual, but are not themselves explained in this way. When Aristotle's (...) view is understood in this way, interesting differences and parallels between him and contemporary essentialists emerge. For one, so-called "properties of origin" such as "being born to George and Barbara Bush" are not essential to the individual that has them, on Aristotle's view. Furthermore, understanding Aristotle's view in this way explains why essences are not, as it has often been maintained, merely "career attributes"--properties that an individual has necessarily and at each moment at which it exists. I argue that for Aristotle, essences belong to an individual in virtue of the species to which it belongs, and that Aristotle subscribes to the "species-form" view of essence. I examine and respond to arguments to the contrary that, in both the Metaphysics and the Generation of Animals, Aristotle holds that the essence of an individual substance is an "individual form" unique to that thing, and not shared by any other individual. Aristotle's account of family resemblances, in particular, has been thought by many to present problems for understanding Aristotle's essentialism. In that text it looks like Aristotle gives up on the view that only certain features--the ones that define the species--are essential to an individual when he attempts to explain the phenomena of family resemblance. I conclude with a sketch of a reading of this text that shows Aristotle holding an account of family resemblances that is consistent with the view that only certain features--the explanatorily basic ones--are part of the essences of individual substances. (shrink)