In the later years of his life, Thomas Hobbes developed an intense interest in the history of Christian heresy, an interest which informed half a dozen of his manuscripts and publications. These heresy writings have typically been studied within the context of Restoration church politics. This article offers a broader account of the significance of these writings. It reads them as extensions of Hobbes’s longstanding project of theological reform. Hobbes’s heresy writings were not merely intended to defend him from prosecution under English law. They also constituted an audacious and risky reassertion of the assault on Trinitarian orthodoxy that Hobbes had supposedly retracted in the Latin translation of Leviathan. The article concludes by considering what this interpretation might tell us about Hobbes’s vacillating commitment to religious toleration.