Around the world, people are faced with crisis after crisis, from the COVID-19 pandemic and climate change-induced fires, floods, and storms to the ongoing horrors of mass incarceration, brutal immigration enforcement, endemic gender violence, and severe wealth inequality. As governments fail to respond to—or actively engineer—each crisis, ordinary people are finding bold and innovative ways to share resources and support vulnerable members of their communities. This survival work, when done alongside social movement demands for transformative change, is called mutual aid. This book is about mutual aid: why it is so important, what it looks like, and how to do it. It provides a grassroots theory of mutual aid, describes how mutual aid has been a part of all larger, powerful social movements, and offers concrete tools for organizing, such as how to work in groups, decision-making process, how to prevent and address conflict, and how to deal with burnout. Mutual aid isn’t charity: it’s a form of organizing where people get to create new systems of care and generosity so we can survive.