Which part was played by science in the French “civilizing mission” ? From the 1880s, the interests of science were combined with those of national prestige. Colonization was undertaken in the name of science. To civilize, in official French colonial ideology, was to bring the benefits of science, just as for other countries, it was to bring the benefits of religion or free trade. The “civilizing mission” thus managed to combine elements of Eurocentrism and scientism. It represented a cultural consensus from the 1880s until the 1930s, and conditioned many generations of French scientists in their training, in their scientific practices, and in their mentalities. Many societies and institutions were established to organize colonial scientific activities : learned societies (Geographical Society, Anthropological Society, and so on), the Association Science and Colonies, the Colonial Academy of Science, the Colonila Scientific Congresses,...The aim of this essay is to analyse this colonial function of science, far to be only a technical tool. It is to describe how it occupied such a central part in colonial ideology and policy from the 1880s, with the name of "civilizing mission"