This article explores the creation of a national index of sexist violence in Argentina in 2016 as an example of data activism in the Global South. Drawing upon a qualitative content analysis of press coverage and activist posts on social media, as well as interviews with activists, it describes the context of the #NiUnaMenos feminist mobilization and the collection “from below” of data on gender violence. This study illustrates how activists in the Global South can appropriate technology and promote new uses that not only respond to their local and immediate needs but also contribute to the production of alternative imaginaries on big data in the longer term. Moreover, the article positions women’s movements as an essential component of current social movements in Latin America.