Aristotle’s writings on animals comprise approximately a quarter of his surviving works. There are three lengthy treatises entitled Historia Animalium, On the Parts of Animals, and On the Generation of Animals. Other works on animals include On the Movement of Animals and On the Progression of Animals. In addition to these, a number of short discussions, collectively entitled the Parva Naturalia, focus on the capacities of living beings such as perception, breathing, and sleep. These works form what has been referred to by scholars in the last fifty years as the “biological corpus” of Aristotle. In them we find rich and varied discussions about anything from keenness of sight to egg laying, from parenting skills to dreaming. Much of the content of these works has been consistently marginalized in the history of philosophy.1 Bringing to light Aristotle’s biology as part of his philosophy is the main focus of this collection. This introduction will touch on the history, content, and methodology of these works and Aristotle’s key ideas on the science of living beings.