This dissertation explores the intellectual, cultural, and political history of knowledge in the late-medieval and early modern Ottoman context by examining the fifteenth-and sixteenth-century Ottoman astrological corpus. This corpus consists primarily of taqwīms (almanac-prognostications), occasional horoscopes, textbooks imparting astrological principles, and the examples of the zīj literature written in Persian and Ottoman Turkish. This dissertation argues that exploring hitherto neglected astrological sources and visiting the lives of hitherto marginalized astral experts (munajjims) provides important insights into the intersecting dynamics of science, politics, and culture in the late-medieval and early modern Ottoman and Islamicate culture. This study consists of three major parts, each undertaken with a combination of different historiographical approaches. The first part (Chapter 1) examines the intellectual and cultural history of astrological practice in the late-medieval and early modern Islamicate culture. I argue that contrary to the scholarly convictions in the historiography of Arabic science, astrology retained its prestigious status as a learned discipline with complex astronomical and mathematical underpinnings. The heightened interest during this period in the eastern Islamic lands in conducting observational enterprises and updating the available celestial data in the astronomical tables was inextricably related to the need for undertaking more accurate practice of astrology. The second part (Chapter 2 and Chapter 3) of the dissertation focuses on the social history of munajjims in the Ottoman realm and tries to understand the complex social and patronage dynamics within which they functioned. By tracking their career trajectories from their vocational training to professional service, this part addresses several questions about the contents, mechanisms, and institutional structures of learning and practicing astrologically valid knowledge. The third, and the last, part (Chapter 4 and Chapter 5) examines in a detailed fashion the personal and political implications of the ever-changing textual contents and constituents of almanac-prognostications (taqwīm) and other occasional horoscopes. By documenting the political significance and public recognition of astrological prognostications, this part demonstrates the ability of often-marginalized astrological texts to provide surprising complementary details about the early modern Ottoman political culture.