The Popular Republican Union (French: Union populaire républicaine, UPR) was a Christian democratic party in Alsace, France during the Third Republic. Founded in 1919, the UPR attracted most of the Alsatian adherents of the Catholic Centre Party in Alsace-Lorraine, formed since the mid-1890s, forming with 31% of the seats the strongest party in the Landtag of the former Alsace-Lorraine. The UPR became the dominant party in Alsace during the Interwar era.