This paper focuses on the process of region formation and its interrelation with agency and regional identity. The region formation processes of two regions in Flanders (Belgium) were analysed, using a framework assessing the institutionalisation of regions. Based on semi-structured interviews and policy documents, the analysis confirmed the usefulness of the concept of institutionalisation to understand and visualise the evolution and ongoing dynamics of region formation processes. The analysis reveals the importance of the dynamic and interactive character of the different aspects of the framework of institutionalisation. The region formation processes in the two regions also indicate the importance of individual catalysts, people who stimulate synergies between the different aspects of the process, resulting in the (re)production of the region and its identity. Regional attachment or ‘regional identity’ was indispensable in the actions of these catalysts and the region formation processes.