 What is presented here is just a brief report of the interesting philosophical views that medieval Muslim thinkers developed about mathematics. It is by no means exhaustive. Many aspects of the views I discussed here have not yet been studied in the secondary literature. It is no exaggeration to say that the philosophy of mathematics of many Muslim philosophers has not been sufficiently addressed by contemporary historians of philosophy. But I hope that the things brought together in this entry have shown that the Islamic tradition is a rich resource for innovative ideas and theories pertinent to the philosophy of mathematics (and not—as is usually thought—only to the technical aspects of mathematics).