This up-to-date review of this expanding field features conceptual chapters that provide readers with an overview of the specific principles and tools used in the development of molecular non-noble metal catalysts, such as the use of cooperative/redox non-innocent ligands, computational methods, and proton-coupled electron transfer (PCET) reactions. Reaction-specific chapters then typically focus on the use of non-noble metal catalysts in general or of one specific base metal for a specific reaction or highly related set of reactions. A must-have for researchers in the field of homogeneous catalysis and molecular synthesis, both in academia and in industry.