Footfall contains the highest harvestable biomechanical energy from the human body, which can attain 67 W, showing great potential as a pervasive and sustainable power source for wearable bioelectronics in the era of the Internet of Things. Developing an effective technology for robust and efficient energy harvesting from human walking remains highly desired. Here, we present a waterproof smart insole, based on a triboelectric nanogenerator, for highly efficient and robust human biomechanical energy harvesting. This insole was rationally designed as a composite structure to fully utilize the pressure distribution of a footfall for wearable electricity generation and to deliver a power output reaching 580 μW. The insole was additionally able to withstand use in harsh environments, including pluvial conditions, without affecting the power output consistency. A total of 260 light-emitting diodes were lit up with perspiring feet and water on the floor, and a capacitor of 88 μF was charged to 2.5 V in 900 s. This work represents a practical approach to developing a highly efficient and robust smart insole that can be used as a sustainable power source for wearable bioelectronics.