Designing the hydrogen evolution reaction (HER) electrocatalysts by tuning the micro/nano structure and optimizing composition to overcome the sluggish HER kinetics have fueled intensive research interests in recent years. Herein, the Co and CoP nanograins embedded in porous nitrogen-doped carbon nanofibers (Co/CoP@NC) are prepared by a controllable electrospinning method and subsequent thermal treatments as the wide-pH HER electrocatalysts. Owning to the prominent merits of strong synergistic relationships between Co and CoP nanoparticles, N-doped carbon configuration, and the interconnected three dimensional (3D) porous carbon network, the Co/CoP@NC nanofibers exhibit robust HER activity with affording an overpotential of 117 mV in acidic and 180 mV in alkaline media to deliver the current density of 10 mA cm(-2). As a practical application, when integrated the Co/CoP@NC/Ni foam cathode with the NiFe layered double hydroxides/Ni foam anode (NiFe-LDH/Ni foam), the electrolyzer can afford the cell voltage of 1.62 V to deliver the current density of 10 mA cm(-2), as well as ultralong lifetime of 60 h in alkaline medium, providing a viable alternative to the noble-metal electrocatalysts for water splitting.