Two 17th century Venetian women, Lucrezia Marinella and Arcangela Tarabotti, argued that the power men exercised over women should be conceptualized as tyranny.  Their aim in so doing was to expose that power as a political injustice.  In disputing the claim that the authority of men over women was grounded in nature they contributed to making sexual inequality visible as a political phenomenon. In this paper I sketch the context in which Marinella and Taribotti wrote, and explore their different claims and arguments.  I argue that in insisting on the natural, divinely bestowed liberty and rational capacity of women in their criticism of masculine tyranny they laid the foundation for later efforts to gain the rights of political participation for women.