Flavin-dependent “ene”-reductases can generate stabilized alkyl radicals when irradiated with visible light; however, they are not known to form unstabilized radicals. Here, we report an enantio­selective radical cyclization using alkyl iodides as precursors to unstabilized nucleo­philic radicals. Evidence suggests this species is accessed by photo­excitation of a charge-transfer complex that forms between flavin and substrate within the protein active site. Stereo­selective delivery of a hydrogen atom from the flavin semi­quinone to the prochiral radical formed after cyclization provides high levels of enantio­selectivity across a variety of substrates. Overall, this transformation demonstrates that photo­enzymatic catalysis can address long-standing selectivity challenges in the radical literature.