This Cluster Coordination Reference Module1 is about the basics of cluster coordination in non-refugee situations. It is compiled in response to a request by the IASC as a reference guide for practitioners to facilitate the work through which humanitarian outcomes can be improved. It outlines key concepts and draws attention to existing guidance, wherever relevant. This reference module will be reviewed periodically based on feedback from the field. This module covers both large-scale responses identified within the IASC Transformative Agenda3 as ‘level 3’4 and smaller scale (‘non-level 3’) responses.