This chapter examines the origins of the Home Rule movement during the 1870s focusing on Isaac Butt’s pioneering vision of federalism as a constitutional solution to Ireland’s governance. The analysis reveals how Butt’s Irish Federalism (1870) proposed a radical reimagining of the United Kingdom’s structure,creating national parliaments for local affairs while maintaining an imperial parliament for common concerns. The chapter explores the intellectual foundations of this federalist model, showing how it emerged from earlier debates about representation while attempting to reconcile Irish autonomy with the Union. Butt’s federalist framework was fundamentally unionist in intent, seeking to perfect rather than dissolve the imperial connection. However, as the chapter traces, this nuanced constitutional position became obscured as the Home Rule idea was adopted by more radical voices who reinterpreted it along separatist lines. The chapter illuminates this pivotal transitional period when the constitutional experimentation of federlaism gave way to the more rigid nationalist/unionist binaries that would dominate Irish politics by the 1880s.