<p>Ni Una Menos (NUM) is a social movement that since 2015 has spread through Latin America as a response to continuing problems of femicides and gender-based violence. NUM challenges gender power relations embedded in the machista culture, which top-down approaches within mainstream gender and development approaches (GAD) have overlooked. To date, most studies of NUM have focused on the movement in Argentina, and its major public actions. Few studies have sought a holistic understanding of how the movement contests Gender Based Violence (GBV) on a day-to-day basis. This research involved a case study of the NUM movement in Arequipa, Peru. I undertook a mixed methods approach, placing this in context of GAD and social movement theories. I worked with NUM Arequipa activists to understand the movement and its strategies in the local context; and with students to explore their knowledge about, and response to, NUM Arequipa’s strategies. NUM Arequipa practised two forms of activism. The first - ‘traditional’ activism’, raised awareness and challenged machista sociocultural structures through media, public campaigns and education. These strategies complemented international GAD practice by challenging unequal gender relationships and incorporating male participation. The second - ‘quiet’ or ‘everyday’ activism - focused on providing support and advocacy for victims of GBV, and a commitment to empathy, care and justice. For both types of strategies, social media and connections to local organisations were important. However, NUM Arequipa, with its non-feminist public identity and quiet activism, found challenges distinguishing itself from other ‘loud’ feminist NUM groups. This confusion meant that students had limited awareness of NUM Arequipa’s specific activities and achievements. The thesis concludes that grassroots movements like NUM Arequipa, alongside more explicitly feminist and confrontational forms of social movements, are essential to eradicating GBV because they can work through relationships to make short-term change in people’s lives while also challenging patriarchal and machista structures in ways that are sensitive to the sociocultural context.</p>