The article sets out to gauge the usefulness of the concepts of legitimacy, sovereignty and nation in theorising a specific, South-East Asian case of nation building. It looks at the interplay between nation building and regionalist ideology inVietnam, within the context of the Association of South-East Asian Nations (ASEAN). As one of the world’s last communist states, the way in whichVietnam has reconciled hard-won sovereignty with regionalisation is all the more intriguing. The article distinguishes the state-led ideology of regionalism from the macro-level process of regionalisation in charting how sovereignty, legitimacy and nation are constructed in theVietnamese case,with a view to drawing parallels with experiences in other regions....