The ancient world's relationship with animals reveals attitudes toward nature, human exceptionalism, and the moral status of non-human life that are in some ways more sophisticated than later Western traditions.

Aristotle's biological works — the History of Animals, Parts of Animals, Generation of Animals — constitute the most systematic ancient investigation of animal life. His observations are a mixture of careful direct observation and uncritical transmission of anecdote and folklore, but the careful parts are remarkably good. His description of the development of the chick embryo, for example, was not surpassed in accuracy until the invention of the microscope.

Pythagorean and later Platonic arguments for vegetarianism, based on belief in metempsychosis (the transmigration of souls between humans and animals), represent the most systematic ancient challenge to the instrumental use of animals. Porphyry's On Abstinence from Killing Animals is the most comprehensive ancient case for animal welfare and remains philosophically interesting.

The Roman arena's systematic slaughter of exotic animals — the numbers in Augustan and later accounts run to the thousands for single events — is the most extreme ancient exploitation of animals. Its environmental consequences — the depopulation of lion populations in North Africa, the near-extinction of the North African elephant — are documented in the archaeological and historical record.