Since Breslow's seminal discovery of Mn porphyrin-catalyzed amination of cyclohexane, Mn tetrapyrroles have emerged as an important platform for nitrene transfer catalysis. The combination of nitrene precursors, such as iminoiodinanes or N-haloamides, and Mn(III) porphyrin catalysts enables nitrene transfer to C-H bonds and olefinic substrates to afford amines and aziridines, respectively (Figure ). Enantioselective nitrene transfer catalysis has been realized using D4-symmetric chiral Mn porphyrin catalysts. More recently, White et al. have developed related Mn(III) phthalocyanines as highly active catalysts for aliphatic C-H amination. In analogy to metalloporphyrin-supported metal oxo intermediates in C-H hydroxylation catalysis, the developed nitrene transfer catalysis is proposed to proceed via the intermediacy of reactive high-valent Mn nitrenoids. Figure 1. Mn tetrapyrrole-catalyzed nitrene transfer catalysis has been applied to both C-H amination and olefin aziridination reactions. Electrophilic Mn nitrenoids are proposed to mediate this family of nitrene transfer reactions.