This dissertation examines documentary cinema in Socialist China as an emerging technology of mass politics, a new medium for creating political imaginaries and writing history, and a global vernacular connecting China to other revolutionary and modernizing cultures. At the center of my investigation is documentary cinema's capacities to work across boundaries between reality and fiction, between physical and metaphysical worlds, and between a historical world bound by its materiality and a revolutionary world mobilized to take leaps into a brighter future. I argue that these capacities made documentary a particularly relevant media for socialism for both epistemological and historiographical reasons. Epistemologically, documentary brought together the empirical and the ideological, both fundamental to a Marxist quest for truth. Historiographically, documentary's deep bond to the present moment and its capacity for temporal re-structuring and mass mobilization allowed it to intervene radically into the making and writing of history, particularly in a society engaged with engineering its own transformation. Using visual archives only recently made available, the dissertation's wide-ranging discussions include how documentary re-enacted the civil war upon the founding of the PRC, documented "tomorrow" during the Great Leap Forward, created mass passions for diplomacy in the 1960s, and enabled a poetics of mourning and testimony in the immediate years after the Cultural Revolution. / East Asian Languages and Civilizations