We report the first observation of electroabsorption in GaAs/GaAlAs multiple quantum well structures. We have been able to induce Stark shifts for room‐temperature exciton resonances of ∼10 meV for applied field ∼1.6×104V/cm in a sample with 96‐A˚ GaAs layers, giving large changes in optical absorption (e.g., a factor of 5 or ∼4×103cm−1increase). This should permit optical modulators with micron path lengths and potentially very fast operation.