We examined proactive (early restraint in preparation for stopping) and reactive (late correction to stop ongoing action) motor response inhibition in two groups of participants: professional athletes ( n = 28) and nonathletes ( n = 25). We recruited the elite athletes from Belgian national taekwondo and fencing teams. We estimated proactive and reactive inhibition with a modified version of the stop-signal task (SST) in which participants inhibited categorizing left/right arrows. The probability of the stop signal was manipulated across blocks of trials by providing probability cues from the background computer screen color (green = 0%, yellow =17%, orange = 25%, red = 33%). Participants performed two sessions of the SST, where proactive inhibition was operationalized with increased go-signal reaction time as a function of increased stop-signal probability and reactive inhibition was indicated by stop-signal reaction time latency. Athletes exhibited higher reactive inhibition performance than nonathletes. In addition, athletes exhibited higher proactive inhibition than nonathletes in Session 1 (but not Session 2) of the SST. As top-level athletes exhibited heightened reactive inhibition and were faster to reach and maintain consistent proactive motor response inhibition, these results confirm an evaluative process that can discriminate elite athleticism through a fine-grained analysis of inhibitory control.