Drawing on Benedict Anderson's thought‐provoking idea that nationalism is less an ideology than a form of cultural expression (Anderson 1991: 7), this themed section explores nationalism in Southeast Asia. Here, as elsewhere, the enactment of a nation‐state's sovereign integrity through identity and citizenship cannot be exclusively defined and limited by state territoriality. Premodern inter‐regional connections and broad patterns of human mobility remain an important feature of contemporary Southeast Asia (Amrith 2011; Castles 2004). For many people, everyday life continues to take place in a social space that transgresses borders or (selectively) resists the encroachment of the nation‐state. The border is clearly not only a physical site but also part of a multifaceted nation‐building process – understood here as state‐legitimating nationalism – that has emotional and material manifestations (Johnson et al. 2011). Turning a critical gaze towards the physical margins of the nation‐state, this themed section proposes to go beyond the ‘territorial trap’ (Agnew 1994) of a neatly bounded political entity to focus on selected Southeast Asian sites of resistance and transgressive practice.