The handbook systematically addresses the topic of informal learning from an international perspective and through various theoretical, methodological, and disciplinary approaches. Learning in an individualized and increasingly globalized society is both temporally and spatially unbounded and cannot be reduced to individual life phases or to institutionalized or organized settings. The handbook on informal learning engages with this discussion and examines different facets of the topic from an interdisciplinary and international viewpoint. It provides a systematic overview of the history, key concepts, theory, empirical evidence, international discourse lines, and research methods.