In this Communication, we report the topotactic fabrication of self-supported nanoporous cobalt phosphide nanowire arrays on carbon cloth (Cop/CC) via low-temperature phosphidation of the corresponding Co(OH)F/CC precursor. The CoP/CC, as a robust integrated 3D hydrogen-evolving cathode, shows a low onset overpotential of 38 mV and a small Tafel slope of Si mV dec(-1), and it maintains its catalytic activity for at least 80 000 s in acidic media. It needs overpotentials (eta) of 67, 100, and 204 mV to attain current densities of 10, 20, and 100 mA cm(-2), respectively. Additionally, this electrode offers excellent catalytic performance and durability under neutral and basic conditions.