This is the first full academic study of the political thought of the French regionalist movement in the Belle Epoque. Julian Wright has examined the private papers of Jean Charles-Brun, founder of the Federation Regionaliste Francaise, in detail. He has rethought the conceptual basis of regionalism through Charles-Brun's intellectual biography, showing that it penetrated the political debates of the period as a commonplace in Republican arguments about state reform. Despite the often made association of regionalism with the right, Dr Wright reveals the diversity of political views expressed, and demonstrates that the connection to left-wing federalism ws emphatically present in the intellectual background. Interwoven with this discussion is an examination of the personal mission of Charles-Brun. He saw himself as a reconciler, using his regionalism within a mission to heal the divisions of French politics and society. He argued that France's instability stemmed from an obsession with reforms that followed a priori political models, and that politicians who sought to rethink the shape of the Republic needed to attend to the cultural or economic realities expressed in France's regions. Charles-Brun and his regionalist movement continue to have resonance in current debates about decentralization in France.