Iron catalysis is a growing area of research, as seen by an exponential increase in the publication activities on the topic. This introductory chapter provides a historic overview of the development of iron catalysis including some notable milestones. The advantages of iron, i.e., its abundance, low price, and relative nontoxicity, are discussed, and an overview of the main type of reactions catalyzed by iron is outlined. The advances of heterogeneous iron catalysis (which is not covered in this volume) are exemplified with a few notable cases. Finally, the potential impact of metal impurities in iron sources on the catalytic activity is discussed.