Stand up paddle boarding (SUP) is a rapidly growing sport and recreational activity in which little scientific research exists. A review of the literature failed to identify a single article pertaining to the physiological demands of SUP competition. The purpose of this study was to conduct a performance analysis of a national level SUP marathon race. Ten elite SUP athletes (6 male, 4 female) were recruited from the Stand Up Paddle Surfing Association of Australia to have their race performance in the Australian Titles analyzed. Performance variables included SUP speed, course taken and heart rate, measured with a 15Hz GPS unit. Results demonstrated that there was a variation in distance covered (13.3km-13.9km), peak speed (18.8km/hr-26.4km/hr) and only moderate correlations (r=0.38) of race result to distance covered. Significantly greater amounts of time were spent in 5-10km/hr speed zones (p<0.05) during the race. Peak heart rate varied from 168-208bpm amongst the competitors with the average heart rate was 168.6±9.8bpm. Significantly higher durations were spent in elevated heart rate zones (p<0.05) with participants spending 89.3% of their race within 80-100% of their age-predicted HRmax. Marathon SUP races appear to involve a high aerobic demand, with maintenance of near max heart rates required for the duration of the race. There is a high influence of tactical decisions and extrinsic variables to race results. These results provide a greater understanding of the physiological demands of distance events and may assist in the development of specialised training programs for SUP athletes.