Abstract: We have converted nanoscale mechanical energy into electrical energy by means of piezoelectric zinc oxide nanowire arrays. The aligned nanowires are deflected with a conductive atomic force microscope tip in contact mode. The coupling of piezoelectric and semiconducting properties in zinc oxide creates a strain field and charge separation across the nanowire as a result of its bending. The rectifying nature of the Schottky barrier formed between the metal tip and the nanowire leads to electrical current generation. The efficiency of this piezoelectric power generator is estimated to be 17% to 30%. This approach has the potential of converting mechanical, vibrational, and/or hydraulic energy into electricity for powering nanodevices. The basic principles and potential applications are reviewed.