An optoelectronic effect based on Faraday or Kerr rotation and the quantum‐confined Stark shift is demonstrated. It is novel in that the degree of rotation is controlled by anelectricfield as opposed to amagneticfield. By applying an electric field to a quantum well structure, the Faraday rotation can be tuned into resonance, thereby varying the rotation angle of plane polarized light. We have observed a resonant rotation of 10° in GaAs at a magnetic field of 1 T. By applying a gate voltage of 2 V to a GaAs/AlGaAs superlattice structure, we observed a change in rotation of 1.3° at 2 K. The Faraday–Stark effect could be useful in electrically controlled light switches and high‐speed optical modulators. ©1996 American Institute of Physics.