Irish science fiction is a relatively unexplored area for Irish Studies, a situation partially rectified by the publication of Jack Fennell's Irish Science Fiction in 2014. This article aims to continue the conversation begun by Fennell's intervention by analysing the work of Belfast science fiction author Ian McDonald, in particular King of Morning, Queen of Day (1991), the first novel in what McDonald calls his Irish trilogy. The article explores how McDonald's text interrogates the intersection between science, politics, and religion, as well as the cultural movement that was informing a growing sense of a continuous Irish national identity. It draws from the discipline of Science Studies, in particular the work of Nicholas Whyte, who writes of the ways in which science and colonialism interacted in late nineteenth and early twentieth-century Ireland.