An electrochemical aliphatic C-H amination strategy was developed to access the important heterocyclic motifs of pyrrolidines and piperidines within a uniform reaction protocol. The mechanism of this unprecedented C-H amination strategy involves an anodic C-H activation to generate a benzylic cation, which is efficiently trapped by the nitrogen nucleophile. The applicability of the process is demonstrated for 40 examples comprising both 5- and 6- membered ring formation.