We introduce the concept of embedded legal activity to capture the ways in which lawyers and legal organizations can become intertwined in the ongoing activities of social movements. Embedded legal activity is characterized by diverse issues and venues and comprises legal activities that help support movement infrastructure, close coordination between movement lawyers and other activists, and responsiveness to constituent needs. Investigating a comprehensive data set on legal activity during the southern civil rights movement, we identify forms of legal activity beyond the typical focus of legal mobilization, including defense for movement participants charged with misdemeanors and other crimes, movement assistance on organization‐level legal matters, and general legal aid to movement constituents. These were by far the more common types of legal activity and emerged from the embeddedness of lawyers in a mass movement. We argue that embedded legal activity is likely where movements prioritize grassroots leadership and community organizing and face significant countermobilization, hostile legal and political opportunity structures, and substantial social and economic inequality.