Slavery was a widespread phenomenon in much of pre-colonial Africa but Mauritania stands out as one of the few African countries where it persisted as an entrenched institution even in post-colonial times. Mauritania also offers a rare example of an emancipation movement founded and run by slaves, ex-slaves and descendants of slaves.1 This pioneering social movement enabled people of servile origins to carve out a place for their protest actions in the public sphere. Previously, there had been isolated cases of slave revolts but El-Hor, an organization founded in March 1978 by activists of slave descent, developed into a social and political movement that ultimately entered the corridors of political power. El-Hor ('freeman' or 'emancipated' in Arabic) aimed to further the 'liberation and emancipation' of the 'heirs of slavery'.2 This chapter does not intend to primarily document the history of this struggle as such, even though it is not widely known. Instead, it analyzes the transformations undergone by the Haratine movement since its first actions in 1980. To this end, I describe the trajectory of the collective action as it developed at the interface between society, politics and the struggle for civil and human rights. The focus is on the movement's origins and the successive changes in its form of organization, types of actions and the outcome of its activism.