BACKGROUND: The purpose of this study was to compare the match demands of officiating 15-a-side rugby union at different competitive levels. METHODS: Data was collected using Global Navigation Satellite Systems from 21 referees during 82 competitive rugby union matches across three different competitive levels: 1) professional; 2) semi-professional; 3) amateur. RESULTS: Compared with referees at the professional and semi-professional levels, referees at the amateur level covered less total distance (P=0.005). Additionally, these referees covered less distance jogging, and at low and medium intensity (all P<0.05), and had less time between repeated high-intensity efforts (P<0.001). Furthermore, compared with referees at the semi-professional and amateur levels, referees at the professional level had a higher sprint duration and covered more distance sprinting (all P<0.05), and achieved a higher maximal speed during the longest repeated high-intensity effort or “worst-case scenario” (P=0.026). The professional level referees also displayed a lower average heart rate (P<0.001), spent a higher percentage of time at <60% HRmax (P<0.001), and a lower percentage of time between 71% and 80% HRmax (P=0.004). Finally, external and internal load were strongly correlated for referees at the semi-professional level only (r=0.75, P<0.001). CONCLUSIONS: Overall, the findings demonstrate that refereeing 15-a-side rugby union is more physically demanding at higher competitive levels, particularly in terms of high-intensity efforts. The results provide important information for practitioners involved in the physical preparation and training of rugby union referees.