The chronostratigraphy of the Rhine’s main terrace along the Middle Rhine Valley (MRV) is poorly constrained. This study fills this gap by using electron spin resonance (ESR) dating of quartz grains collected from the famous Kärlich site. Consistent ESR results date this terrace to ~1.5 Ma and have far-reaching implications as they numerically constrain, for the first time, the aggradation time of key terrace deposits along the MRV, providing new insights into the Rhine’s Quaternary evolution.