This article offers the first comparative study of Thomas Hobbes and John Locke’s readings of the Biblical figure of Jephthah the Gileadite and, in particular, the latter’s notorious appeal to God that leads to the killing of his own daughter. To outline its argument, I focus on a critical moment in Hobbes and Locke’s corpuses where they both appeal to Jephthah’s vow to support their theories of sovereign right: Hobbes’ account of the right to punish in Leviathan and Locke’s account of the right to go to war in the “Second Treatise of Government.” If Hobbes and Locke’s readings of Jephthah differ considerably – the one focusing on Jephthah’s daughter, the other on Jephthah himself; the one exploring domestic political theory, the other international relations theory; the one seeking to legitimize the right to punish, the other the right to go to war – I contend that both see Jephthah’s story as an allegory for the origins of sovereign violence in self-sacrifice or even martyrdom. For Hobbes and Locke, Jephthah’s fate becomes a kind of arcane theological paradigm for sovereign killing: what begins as the religious power to die ends up as the political power to kill. In the obscure story of Jephthah the Gileadite, then, I conclude that Hobbes and Locke set in motion what we might call a martyrological machine at the core of the modern liberal state. What if liberalism is constituted less by its professed love of “life” – private interest, private property, self-preservation, self-determination – than a willingness to sacrifice everything and die?