De Selby (spelled "de Selby" in The Third Policeman and "De Selby" in The Dalkey Archive) is a fictional character originally created by Flann O'Brien for his novel The Third Policeman in which the nameless narrator intends to use the proceeds of murder and robbery to publish his commentaries on de Selby – a savant who theorizes, among other things, that the earth is actually shaped like a sausage.