We report a facile and large-scale solution fabrication of cuprous oxide (Cu2O) nanowires/nanorods and 3D porous Cu2O networks and their application as photocathodes for efficient solar water splitting. The growth mechanism and structural characterization of 3D porous Cu2O networks are studied in detail. The photocathodic performance of Cu2O electrodes prepared under different growth conditions is investigated in a pH-neutral medium. The porous Cu2O network photocathodes exhibit large photocurrent, high spectral photoresponse, and incident photon-to-current efficiency compared with Cu2O nanowire/nanorod photoelectrodes. The photoelectrochemical stability of the 3D Cu2O network is significantly improved by applying multi-layer metal oxide protection.