Il s'agit des actes du colloque international sur « Les Semaines Sociales de France, 1904 - 2004 » organisé par le professeur Jean-Dominique Durand à Lyon en octobre 2004./// This text studies the development of the Catholic Congresses since 1848 and stresses the links which were established with the Semaines Sociales, since their creation in Lyon in 1904. Before the First World War, the rise of nationalism on both sides of the Rhine barred the development of regular contacts. After the Second World War, leaders of the Semaines Sociales and members of the Central Committee, which was in charge of organising the Catholic Congresses, met from time to time until the cessation of the Semaines Sociales in 1973. Nevertheless, it was only when the...