Low temperature (2 K) photoluminescence (PL), PL excitation (PLE), and resonant excitation (RE) measurements on a very high quality, 150‐Å‐wide GaAs/Al0.3Ga0.7As multiquantum well structure are reported, with a focus on exciton localization effects. The PL spectra show evidence of effective submonolayer well width fluctuations. Excitons observed via RE are found to be predominantly localized; i.e., they decay from the same effective well‐width region in which they are formed, while both localized and delocalized excitons are observed in PLE measurements. Delocalized excitons are free to diffuse to differing effective well‐width regions which are energetically accessible. These results are supported by time‐resolved PL measurements, which show essentially identical time‐responses for differing effective well‐width regions under resonant excitation conditions, thereby demonstrating the localized nature of resonantly created excitons.