This essay focuses on the origin stories and evidence we have for the Lipizzaner and the Thoroughbred as two different models of breed creation. By reading these stories “in to one another,” I expose both the complexity of definition and the definitional slippage that inevitably accompany stories of purity. One, the Lipizzaner, was dynastically forged within the Habsburg monarchy and empire. The other, the so-called “English” Thoroughbred, was the product of commercial enterprise by English and Irish peers and gentlemen, with support from the royal houses of Stuart, Hanover, and Windsor. Exposing the complexity of definition and definitional slippage associated with breed creation, I argue, these two breed stories reveal the paradoxes at the heart of the concept of equine “purity,” especially when read together in the light of attempts at crossbreeding between them.