Nearly monodisperse single-crystalline In(OH) 3 nanocubes were successfully synthesized using In(NO 3 ) 3 ⋅4.5H 2 O as indium source in the presence of urea and cetyltrimethyl ammonium bromide (CTAB) by a two-step hydrothermal process: the stock solution was heated at 70 °C for 24 h and then at 120 °C for 12 h. The structure and morphology of the resultant In(OH) 3 samples were determined by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The results revealed that most of as-synthesized In(OH) 3 nanocubes were uniform in size, with the average edge length of ∼700 nm. The influences of the reaction temperature, the reaction time, the mineralizer, and the surfactant on the morphology of the obtained products were discussed in detail. Room-temperature photoluminescence (PL) spectrum of the In(OH) 3 nanocubes showed a peculiar strong emission peak centered at 480 nm. Furthermore, the photocatalytic properties of the In(OH) 3 nanocubes were tested. It was found that In(OH) 3 exhibited not only higher activity for benzene removal, but also better H 2 evolution from water than the commercial Degussa P25 TiO 2 .