Efforts to transcend island histories in Irish historiography have predominantly centered a narration of white settler pasts as an outer boundary of Irish history. This article works through the disjunctions between differently situated transnational turns in Irish and Australian historiographies by interrogating metaphors of extension, including “Greater Ireland” in the former historiography. It proposes that to decenter the nation as a historical unit, transnational Irish history requires a critical tension with white settler, and not only Irish, methodological nationalisms. The article surveys the critical possibilities presented by the transnational turn in Irish historiography while questioning its limits, with attention to the paradigm of a transnational Irish revolution. It then flags possible directions for a closer dialogue between transnational Irish history and postnational historiographies of white settler colonialism. An unsettling of discrete historiographical boundaries remains a necessary condition for tracing histories of Ireland beyond, below, and outside the nation.