Mexico's partial democratic transition resulted in widespread violence, human rights violations, inequality, corruption and impunity, frustrating the hopes and aspirations of many sections of society. However, between 2011 and 2016 three major social movements emerged to challenge injustice and demand social change. The Movement for Peace and Justice with Dignity, YoSoy132 and Ayotzinapa 43 were plural non-institutional social mobilizations empowering those victimised and marginalized in the defective democratic settlement. Human rights discourse and digital and social media have become embedded in political discourse and social practice around the world, but their meaning, uses and implications are complex and contested. This thesis examines their role in contentious collective movements in Mexico's specific socio-political context. Qualitative case study research methods are used to examine their dynamic uses and meanings in the three mobilization processes in order to explore their enabling and constraining features. The thesis also draws on the author's previous experience as an international human rights advocate and researcher working on Latin America. The research shows the diverse ways that human rights discourse and digital and social media feature in the practice and meaning of each movement. They are understood to enhance key aspects of civil society mobilization processes, such as strengthening the impact of trigger events and enabling the configuration of skilled support networks, but also to entail certain constraining logics which the movements grapple with to sustain contention. They contribute shaping qualities to the movements but do not monopolise or determine their practices or meaning. These are rooted in the dynamic adaptive approaches of plural actors engaging with their concrete social and political context, creatively using the resources available to mount collective public sphere challenges to the powerholders of Mexico's partial democracy.