From Cross-Border Cooperation to Transfrontierisation: Territorial Dynamics Along the French–Italian Alpine Border

Cross-border regions have become key arenas for experimenting with new territorial configurations, particularly where functional interdependencies challenge inherited administrative boundaries. This article examines how cross-border cooperation contributes to innovative territorial construction along the French–Italian Alpine border, focusing on how territorial actors mobilise the border and how these dynamics relate to the emerging notion of transfrontierisation. The study centres on the urban–mountain system linking Savoie, the Aosta Valley, and the Metropolitan City of Turin, using the A-MONT project (Interreg ALCOTRA 2021–2027) as an empirical entry point. A mixed methodology was applied, combining quantitative analysis of ALCOTRA projects from the 2014 to 2020 and 2021 to 2027 programmes, qualitative fieldwork to local and supra-local actors, and a critical review of recent Integrated Territorial Plans (PITER). The results reveal a pronounced centre–periphery pattern in project participation, persistent disparities in administrative capacity, the development of informal networks that mitigate institutional fragmentation, and the emergence of shared territorial diagnoses. The article argues that these dynamics extend beyond project-based interaction and proposes the concept of transfrontierisation to describe the process through which cross-border cooperation reshapes supra-local networks, stabilises governance arrangements, and fosters shared territorial referents without replacing existing institutional frameworks.