Comprehensive Summary The N–H methylsulfoxidation of sulfoximines using DMSO as a methylsulfinyl source, induced by electrochemistry, has been developed. This method is the first example of an electrochemical reaction in which DMSO serves as a methylsulfinyl source. Unlike previous electrochemical reactions involving DMSO as a substrate, which exclusively proceed via radical mechanisms, this reaction follows an S‐cation pathway. A wide range of N ‐methylsulfinyl sulfoximines were successfully obtained.