Here we demonstrate the feasibility of continuous, self-sustained hydrogen gas production based solely on solar light and biomass (wastewater) recycling, by coupling solar water splitting and microbial electrohydrogenesis in a photoelectrochemical cell-microbial fuel cell (PEC-MFC) hybrid device. The PEC device is composed of a TiO2 nanowire-arrayed photoanode and a Pt cathode. The MFC is an air-cathode dual-chamber device, inoculated with either Shewanella oneidensis MR-1 (batch-fed on artificial growth medium) or natural microbial communities (batch-fed on local municipal wastewater). Under light illumination, the TiO2 photoanode provided a photovoltage of ~0.7 V that shifted the potential of MFC bioanode to overcome the potential barrier for microbial electrohydrogenesis. As a result, under light illumination (AM 1.5G, 100 mW/cm2) without external bias, and using wastewater as the energy source, we observed pronounced current generation as well as continuous production of hydrogen gas. The successful demonstration of such a self-biased, sustainable microbial device for hydrogen generation could provide a new solution that can simultaneously address the need of wastewater treatment and the increasing demand for clean energy.