Significance The migration of cellular populations drives influential and disparate biological processes, from the establishment of embryos to the invasion of cancerous tissues. Its deregulation can lead to improper development or pathogenesis of diseases. While many of the mechanisms that promote single-cell migration have been identified, how cell assemblies coordinate these mechanisms is poorly understood. This manuscript details modes of collective migration and the role of tissue dewetting in generating a symmetry breaking, which drives the spontaneous migration of cell aggregates en masse . This discovery, its corresponding assay, and the establishment of the underlying fundamental physical principles provide a powerful platform for further in-depth studies and insights into biological migration at the mesoscopic scale.