The distinction between native and alien species is a main tenet of various natural sciences, invasion biology in particular. However, it is also a contested one, as it does not reflect the biological features of a species, but only its place of origin and migration history. The present paper offers a brief genealogy of the native/ alien divide and argues that central to this binary is a national thinking that divides the world into distinct (national) units, enclosed by (natural) borders, with a unique (native) population attached to these spatial units. The paper illustrates this argument by looking at two interrelated processes: the nationalisation of nature, by which the national thinking intervenes as an organising principle in determining ecological inclusion/exclusion, and the naturalisation of the nation, through which the nation is given an ontological status. Taken together these two processes confirm the continuing salience of the nation as a b-ordering principle actively constituting both the social and natural world, also in times of anthropogenic changes and increasing people's mobility.