The “Holy Spirit” is a familiar concept in Christianity, but in its original Hebrew construction as Ruah ha-Kodesh, it also plays an active role in classical Rabbinic literature. This dissertation surveys uses of the term Ruah ha-Kodesh in major texts from the Tannaitic period through the Aggadic Midrash and the two Talmuds. Drawing on Scriptural roots, the Rabbis identify Ruah ha-Kodesh as the divinely given power that enables individuals to prophesy. While the term never loses this biblical meaning, the Rabbis take Ruah ha-Kodesh further by personifying it as a metonym for God, and more specifically, as “the divine voice in Scripture.” This dissertation first surveys the historical background of the term in pre-Rabbinic ancient Judaism, and then turns to a detailed textual analysis of its uses as both prophecy and personification in Rabbinic literature. The study notes and examines conventional and formulaic terms associated with Ruah ha-Kodesh. Four major Ruah ha-Kodesh traditions are analyzed in depth over the course of their diachronic development. There are numerous Rabbinic sources that claim that Ruah ha-Kodesh has ended, yet others offer advice on how to achieve it or indicate its existence in the Rabbinic present. The solution to this paradox is that Ruah ha-Kodesh has not gone, but changed. Even as Ruah ha-Kodesh is said to have departed from Israel in her role of inspiring the prophets, she continues to speak actively as part of the ongoing Midrashic dialogue with the Sages. The final chapter examines Ruah ha-Kodesh as a metonym for God, particularly as it contrasts and interacts with other divine metonyms of feminine grammatical gender: the Shekhinah and the Bat Kol. The Shekhinah and Ruah ha-Kodesh are frequently identified, but not identical. The changing role of Ruah ha-Kodesh exemplifies a shift in the locus of divine communication, from prophecy to the Midrashic study of Torah. / text