Water-related energy is an inexhaustible and renewable energy resource in our environment, which has huge amount of energy and is not largely dictated by daytime and sunlight. The transparent characteristic plays a key role in practical applications for some devices designed for harvesting water-related energy. In this paper, a transparent triboelectric nanogenerator (T-TENG) was designed to harvest the electrostatic energy from flowing water for the first time. The output peak-to-peak open-circuit voltage and current density of the T-TENG could reach 10 V and 2 ?A/cm2, respectively, with the flow rate of the tap water of 93 ml/s. The instantaneous output power density of the T-TENG was 11.56 mW/m2 when connecting to a load resistor of 0.5 M?. Moreover, the transmittance of the as-prepared T-TENG was 87.41% with the organic film thickness of 1?m, larger than that of individual glass substrate of 83.41%, which was caused by the organic film acting as an antireflection coating. These results illustrated the potential applications of the T-TENG for harvesting wastewater energy in our living environment and on smart home system and smart car system.