The lactate threshold (LT) is a valuable parameter for setting appropriate exercise intensities. Whether the intensity where the LT occurs is similar in water vs. land treadmill exercise has not been determined. The purpose of this study was to determine LT during aquatic vs. land treadmill running. On separate days, on land and in water (submerged at the xiphoid process), 15 participants performed on a multistage graded exercise treadmill LT test in random order. LT was determined using the DMax method. At LT, no statistically significant differences were identified for running speed (195.3 ± 31.5 m·min-1 land vs. 188.1 ± 22.9 m·min-1 water), lactate concentration (2.6 ± 0.8 land vs. 2.7 ± 0.8 water mmol·L-1). At LT, there were statistically lower (p < .004) water vs. land VO2 values (37.9 ± 5.4 land vs. 35.0 ± 5.4 water ml·kg-1·min-1), and heart rate (HR; 171 ± 14 land vs 159 ± 18 water bpm). The lower VO2 and HR in water may reflect a lower energy requirement due to a decreased body weight support in the water. This is beneficial for those using aquatic treadmills and desiring to achieve threshold-intensity training while lowering the joint-stress caused by land running.