Radical nationalism is a political ideology centred on tying animagined people to a bordered territory. It grows from nationalism’sroot system into a diversity of political manifestations aimedat sealing the people-territory bond. By theorizing radical nationalism,this article outlines a political-ideological approach that opensnew pathways for studying the so-called far right. The article drawson Michael Freeden’s conceptual-morphological theory and delineateshow nationalism’s thin-centred conceptual core – people andterritory – can thicken into a full-bodied political ideology: fromfootball and flags to systemic discrimination, deportations, andmass violence. In response to the empirical observation that radicalnationalism nurtures historical and contemporary actors across theleft-right spectrum, the article offers a political-ideological lens fortranshistorical analyses of various political manifestations thatsprout and flourish from the exclusionary roots of the modernnation-state.