This dissertation argues that the Manchu conquest of China in the mid-seventeenth century transformed several ostensibly “European” sciences in the early modern period. The “Tartar war” between the weakened Ming dynasty (1368-1644), peasant rebels, and the Manchus—a semi-nomadic population from northeast Asia—was experienced first-hand by several Jesuit missionaries proselytising in China. During the unstable interregnum, Jesuits sought patronage from disparate warring factions, offering their astronomical expertise to help various pretenders secure the “Mandate of Heaven” to rule legitimately over China, hoping to ensure their mission’s survival. By engaging with Chinese and Manchu astronomical labourers, reading Chinese treatises on cosmology, agriculture, cartography, history, and moral philosophy, and interacting with scholar-officials and military commanders, Jesuits learned extensively from local technoscientific discourses and practices. Between 1653 and 1658, the Tridentine missionary Martino Martini (1614-1661) served as a “procurator”—responsible for promoting the China mission in Europe—and a representative of the new, Manchu-led Qing dynasty (1636/44-1912). In Europe, Martini published accounts of the Ming-Qing War (1654), China’s geography (1655), and its history (1658) with commercial printers, reaching a wide, interconfessional readership. He courted patronage from powerful Habsburg rulers and defended the Jesuits’ involvement in Chinese sciences and politics at an audience with Pope Alexander VII. As this dissertation contends, Martini’s successful mobilisation of disparate political, religious, commercial, and scholarly networks across a turbulent Eurasia enabled his laudatory accounts of Chinese sciences to convince an extraordinarily wide audience. In turn, during the long eighteenth century, European writers drew—often polemically—on Martini’s accounts of Chinese agriculture, astrology, cartography, chronology, cosmology, ethnography, military cultures, and moral philosophy to articulate new solutions to contemporary technoscientific, social, and political crises. As such, the dissertation argues that Manchu and Chinese cultures of knowledge, mediated by Jesuits, occupied an important and underappreciated role in Enlightenment sciences.