Did few, if any, historical women think very deeply about international relations? Existing surveys and anthologies convey just this impression; women in the past did not think seriously about international politics. This article provides evidence of the scale of historical women's exclusion, analyzing sixty texts in the history of international thought and disciplinary history. It also begins the process of remedying this exclusion, mapping a new agenda for research on the history of women's international thought. Existing work in feminist historiography and new archival research suggests that a diverse array of historical women thought deeply about international relations, but their intellectual contributions have been obscured, even actively erased. To illustrate what can be gained by pursuing a research agenda on historical women's international thought, the article reveals a neglected but at the time extremely important figure in what might be called 'white women's IR', the influential scholar of colonial administration, Lucy Philip Mair. Recent years have witnessed an exciting and cross-disciplinary revival of scholarship on the history of international thought and discipline of International Relations (IR) (Armitage, 2013; Leira and Carvalho, 2015). Yet there are currently no histories of women in the early years of IR, nor a substantial body of scholarship challenging the neglect of women in the 'canon' of international thought. Survey texts and anthologies are still published as if women in the past did not think seriously about international politics. What explains the neglect of historical women? It might be assumed that there simply were no women in the earliest years of the new science that emerged at the end of the nineteenthcentury. Perhaps few, if any, women in the past thought very deeply about relations between peoples, empires, and states. If so, then women's absence from the relevant histories would not require much further examination. The more urgent task would be to decrease the citation gap that disadvantages contemporary women, people of color, and scholars from the Global South, as suggested in the author guidelines for this journal (ISQ, 2017). But what if a diverse array of historical women, that is women writing before the late twentieth-century, had thought deeply about international relations? Recent efforts to address the citation gap for contemporary scholars can do little to recover and analyze historical work that remains unknown. There may even be a persistent connection between the absence of a recognized and respected history of women's thought on international politics and their status in the field today. Robert Vitalis (2015) has recently argued that this is the case for African-American women and men. This article builds on conversations initiated at a CHASE-German Historical Institute workshop in 2015, 'Languages of the Global: Women and International Political Thought', led by the historians Katharina Rietzler, Valeska Huber, and Tamson Pietsch, and continued at a BISA...