<p>Actin cytoskeleton remodelling drives the migration of immune cells and their engagement in dynamic cell–cell contacts. The importance of actin cytoskeleton dynamics in immune cell function is highlighted by the discovery of inborn errors of immunity (IEIs) that are caused by defects in individual actin-regulatory proteins, resulting in immune-related actinopathies. In addition to susceptibility to infection, these often present with a vast array of autoimmune and autoinflammatory manifestations. Here, we review the role of actin subnetworks in the activation and function of lymphoid and myeloid cells. We focus on the mechanisms by which actin defects result in aberrant lymphocyte function, including dysregulation of T cell- and B cell-mediated tolerance and biased cytokine production, which can result in autoimmunity. We also highlight the relationship between actin defects and inflammasome activation&#xa0;and other pathomechanisms in myeloid cells as the underlying cause of autoinflammation. Finally, we discuss future avenues for research and therapeutic intervention based on a molecular understanding of immune-related actinopathies.</p>