Photocatalytic activities for hydrogen evolution of lanthanide zirconium oxides, Ln 2Zr 2O 7 (Ln = La, Ce, Nd and Sm) prepared by a solution reaction method were investigated. Under the illumination of 500 W Xenon lamps, hydrogen gas was clearly evolved in a distilled water suspension of La 2Zr 2O 7, Sm 2Zr 2O 7 and Nd 2Zr 2O 7. Under the visible-light illumination, hydrogen gas was evolved in a distilled water suspension of Nd 2Zr 2O 7 and Sm 2Zr 2O 7. From the photoelectrochemical measurements, the values of the flat band potential were estimated to be −0.64, −0.52, −0.31 and +0.04 eV for La 2Zr 2O 7, Sm 2Zr 2O 7, Nd 2Zr 2O 7 and Ce 2Zr 2O 7, respectively, versus the normal hydrogen electrode (NHE). The values of the band gap energy were calculated to be about 3.52, 2.86, 2.67 and 2.53 eV for La 2Zr 2O 7, Sm 2Zr 2O 7, Nd 2Zr 2O 7 and Ce 2Zr 2O 7, respectively. Due to the effect of 4f orbital electrons, the band gap energy of these compounds becomes narrower than in ZrO 2 and as a consequence, Sm 2Zr 2O 7 and Nd 2Zr 2O 7 show the photocatalytic activity under the visible-light.