Harvesting energy from ambient mechanical motions addresses limitations of traditional power supplies by providing a sustained electric power source. Here, a high-performance rotary triboelectric nanogenerator (r-TENG) is applied in a variety of circumstances to specifically harvest mechanical energy from human body motions. When rotating at 500rmin−1, it can produce an ac electric output that has a current amplitude of 0.75mA and a voltage amplitude of 200V at a frequency of 750Hz. Integrated with structural components that transfer mechanical motions and electric components that achieve power management, the r-TENG is demonstrated as a power source by harvesting energy from foot pedaling, arm swinging and foot pressure. The generated electricity can effectively charge consumer electronics such as a cellphone, which shows the promise of the r-TENG as a power source for portable, wearable and even implantable electronics.