Nanorobots capable of self-propulsion in low Reynolds number fluids would have a big technological impact in many fields. Few known mechanisms are able to propel such devices. Here we demonstrate that helical nanobelts can swim in liquid when actuated by an electric field generated by electro-osmotic force. Moreover, we show these devices achieve speeds at or slightly above those demonstrated by natural bacteria. The helical nanobelts were designed and fabricated with a head and tail to mimic natural micro-organisms such as bacteria and their flagellae. The electro-osmotic propulsion of helical nanobelts might be used as biomedical carriers, wireless manipulators, and as local probes for rheological measurements.