Late transition metal catalysts, such as palladium, rhodium, and iridium, have played key roles in organic synthesis over decades, due to their high catalytic activity and selectivity. More recent studies in this field, however, have experienced a significant paradigm shift towards using non-precious, earth abundant, first-row transition metal catalysts, mainly due to their economic and environmental advantages. To realize high catalytic activity and selectivity using first-row transition metal catalysts, unique design on catalysts, ligands, and/or reacting substrates is often required. In this thematic issue, we would like to shed light on “Cobalt Catalysis” in organic synthesis, because cobalt catalysts not only work as alternatives to precious rhodium catalysts, but often show unique catalytic activities. Recent advances in broad range of cobalt catalysis, such as C–H bond functionalization, cross coupling, asymmetric reactions, biomimetic transformation, polymerization, and others, will be featured.