  This entry is intended as a brief and general introduction to the development of category theory from the beginning of the Middle Ages, in the sixth century, to the Silver Age of Scholasticism, in the sixteenth. This development is fascinating but extraordinarily complex.  Scholars are just beginning to take note of the major differences in the understanding of categories and of how these differences are related to the discussion of other major philosophical topics in the Middle Ages. Much work remains to be done, even regarding the views of towering figures, so necessarily we have had to restrict our discussion to only a few major figures and topics. Still, we hope that the discussion will serve as a good starting point for anyone interested in category theory and its history.