In the face of persistent neglect and denial of the severity of COVID-19 by the administration of President Jair Bolsonaro, residents in many of Brazil’s favelas have been left to organise their own responses to the pandemic. Community leaders have raised funds and volunteers are going door-todoor to distribute food, masks, and hygiene kits, using megaphones to educate residents about mask use, physical distancing, and handwashing. Local journalists are also using social media to counter fake news, and activists are converting schools into isolation wards, facilitating cash transfers, and fighting for the accurate documentation of COVID-19 deaths. Solidarity practices in the favelas have much to teach global and public health experts. Published reports and the insights of eight activists involved in mutual aid whom we interviewed reveal how solidarity practices challenge key assumptions in conventional global health and reveal the merits of social medicine in Latin America and global social medicine. This is an opportune time to underscore a vision of global social medicine that emphasises horizontal cross-community learning and solidarity, the reinvention of democratic civil society, and the creation of infrastructures that support self-determination.