As a geographer, Paul Vidal de la Blache (1845-1918) was concerned about two issues related to politics. On the one hand, he wanted to understand the role of politics in geographical dynamics. On the other hand, he tried to stimulate the political interest for geography in France. In so doing, his goal was to consolidate geography both as a scientific discipline and as a public institution. This double concern was particularly evident when he was promoting the regional reform of France. This paper tries to explain how and why geography and politics influenced each other in Vidal's regionalism.