Homogeneous transition metal catalysis is one of the most promising methodologies for the transformation of CO 2 into value-added chemicals and secondary energy carriers. However, most of the transition metal catalysts used for this purpose are currently based on rare, expensive, and often toxic metals such as ruthenium, rhodium, palladium, or iridium. Copper and iron, two of the most abundant metals in earth's upper crust and both characterized by low toxicity, constitute highly promising alternatives for the monetization of CO 2 in the context of sustainable catalysis. The present work gives a comprehensive overview of all CO 2 activation transformations catalyzed by copper- and iron-based transition metal complexes.