Swaby, R, Jones, PA, and Comfort, P. Relationship between maximum aerobic speed performance and distance covered in rugby union games. J Strength Cond Res 30(10): 2788-2793, 2016-Researchers have shown a clear relationship between aerobic fitness and the distance covered in professional soccer, although no research has identified such a relationship in rugby union. Therefore, the aim of the study was to identify whether there was a relationship between maximal aerobic speed (MAS) and the distance covered in rugby union games. Fourteen professional rugby union players (age = 26 ± 6 years, height = 1.90 ± 0.12 m, mass = 107.1 ± 24.1 kg) participated in this investigation. Each player performed a MAS test on 3 separate occasions during the preseason, to determine reliability and provide baseline data, and participated in 6 competitive games during the early stages of the season. Game data were collected using global positioning system technology. No significant difference (p > 0.05) in total distance covered was observed between games. Relationships between players' MAS and the average distance covered from 6 competitive games were explored using Pearson's correlation coefficients, with MAS performance showing a strong relationship with distance covered during match play (r = 0.746, p < 0.001). Significantly greater (p = 0.001, Cohen's d = 2.29) distances were covered by backs (6,544 ± 573 m) compared with the forwards (4,872 ± 857 m) during a game. Similarly, backs recorded a significantly (p = 0.001, Cohen's d = 2.20) higher MAS (4.9 ± 0.13 m·s) compared with the forwards (4.2 ± 0.43 m·s). Results of the study illustrate the importance of developing high levels of aerobic fitness to increase the distance that the athlete covers in the game.