Hypervalent iodine chemistry is a very active research area in both organic synthesis and natural product chemistry. Hypervalent iodine reagents have been used to perform various oxidative transformations under mild reaction conditions. These reagents have received particular attention since the first reports, in 2005, that they can act as catalysts. Since then, various hypervalent iodine catalyzed oxidative functionalizations, such as oxidations of alcohols and phenols, α-functionalizations of carbonyl compounds, cyclizations, and rearrangements have been successfully achieved. Several catalytic reactions have been developed using hypervalent iodine reagents as catalysts, while in other reactions iodoarenes have been used as precatalyst to generate active iodine(III) or iodine(V) species in situ. This chapter highlights various aspects of hypervalent iodine-catalyzed oxidation reactions, including asymmetric variants. © Georg Thieme Verlag 2018. All rights reserved.