The present study focuses on investigating dreams (for which the Greeks used three different words: oneiros/oneiron, onar and enupnion) and their incursions into Plato s dialogues. Of the approximately twenty-eight dialogues rarely considered apocryphal, in eighteen of them we find many incidences to the irruption of sleep and the process of awakening, to the formation of dreams, as well as to the problem of the differentiation between dream and wake, which is the reason why we consider them philosophical concerns dear to Plato. Although the general objective of this thesis is to propose an overview of the mentioning of dreams throughout the Platonic corpus, our investigation focuses mainly on six dialogues and their respective thematizations of dreams: Theaetetus, Carmides, Republic, Apology, Crito and Phaedo. Our specific aim is to understand the philosopher s doctrine through these incursions, since, as we shall see, if, on the one hand, it shall be made evident the difficulty of finding a criteria capable of discerning illusion and reality, dream and wake, to the Platonic hypothesis of immutable forms an important role in this distinction shall also be assigned. In parallel, we find in these philosophical dramas various accounts of dreams that Socrates had dreamed, which, with the help of the dreamer himself, we are led to investigate. In conjunction with that, we also observe the influence of the Homeric and Hesiodic mythological conceptions of dreams on the Platonic conception of them, as well as his own philosophical reinvention.