This essay argues that the Church of Ireland in the early modern period was a Reformed expression of Anglicanism by investigating a few events in the life and ministry of James Ussher, the Archbishop of Armagh. First, it looks at Ussher’s contributions to the Church of Ireland’s burgeoning Reformed identity by recounting his debate with a well-known Jesuit theologian, which substantiated his vigorously Protestant outlook, and his involvement in composing the Irish Articles of 1615. Second, it looks at how he later attempted to defend Reformed theology in the Church of Ireland from Arminianizing impositions from the Church of England. Finally, it presents an upcoming release of Ussher’s never-before- published lectures in theology, which provide a fresh perspective on his Reformed identity.