The synthesis of nitrogen-containing molecules through carbon-nitrogen (C-N) bond formation is critical for the discovery and preparation of medicines, agrochemicals, and materials. Here, we report the direct insertion of a nitrogen atom into unactivated carbon-carbon double bonds to access aza-allenium intermediates, which can be converted either into nitriles or amidine products, depending on the initial alkene substitution pattern. This operationally simple and highly functionally compatible reaction works on a wide range of unactivated alkenes. PIFA, a commercially available and inexpensive hypervalent iodine reagent, is key to this reactivity. Our mechanistic proposal is supported by chemical trapping experiments, which concomitantly demonstrate the utility of our method to access valuable N-heterocycles. Additionally, our method can be used as a general strategy for synthesizing amides and amines, as well as 15N-labeled molecules.