The influence of the Platonic theory of forms is to be found in nearly all periods in the history of Western philosophy. Much less well known is the fact that in all ages Arabic philosophers also discussed “Platonic forms” in their written works, although they had no access to Plato’s Dialogues. This study analyses how this conception was given doctrinal content without recourse to Plato’s works, and presents the relevant Arabic works in German translation for the first time. They offer a first insight into a branch of the reception of Platonism that has not yet been researched, but which is often clearly influenced by Islam.