There is a surprising number of deformed animal kinds mentioned in Aristotle’s biological works. The number is surprising because, according to the standard understanding of deformed animals in Aristotle, it should be zero. And the number is significant because there are just too many deformed kinds at too many classificatory levels mentioned in too many works to dismiss them as a minor aberration or as an infiltration of folk belief into biology proper. This paper has two goals. The first is to develop an interpretation of deformed animal kinds in Aristotle, which focuses on the meaning of deformity applied to kinds. The second goal is to draw out the consequences of that interpretation for our understanding of Aristotle’s view of normal animal kinds. The paper ends with a brief consideration of what the meaning of deformity tells us about Aristotle’s view of normal animal kinds.