In this thesis, I argue two main points concerning the significance and development of Martin Heidegger's concepts of discourse and language. The first is that his concept of discourse, which for the Heidegger of Being and Time is the human practice of articulating meaning or intelligibility, has often been misunderstood as either (a) simply another name for natural languages, or (b) a wholly prelinguistic and precommunicative phenomenon. I attempt to find a middle way between these two interpretations that, on my view, is truer to the text, and argue that although discourse does sometimes manifest itself prelinguistically, it is also an essentially communicative phenomenon. The second point I argue is that contrary to the usual interpretation of his development, Heidegger's "turn" to "language" in his later works does not constitute an embrace of linguistic idealism, i.e. the belief that one can only encounter as meaningful objects that have been named in one's natural language. Instead, I argue that it remains, like discourse, a prelinguistic phenomenon, and I also note several interesting parallels between the two concepts. I conclude by making some suggestions about what is really at stake in the transition from discourse to language, and argue that the key difference lies in the fact that, for the later Heidegger, the articulation of meaning is no longer primarily a communicative phenomenon rooted in human activity.