We report the facile synthesis of ultrathin beta-FeOOH and epsilon-Fe2O3 nanowires with diameter of 2-3 nm. The beta-FeOOH nanowires show the unique optical properties attributed to the size- and shape-related quantum confinement effect. Upon heat treatment, they are transformed into epsilon-Fe2O3 nanowires, which exhibit the different magnetic properties compared with the previously reported epsilon-Fe2O3 nanostructures synthesized in silica matrices. The epsilon-Fe2O3 nanowires also exhibit high catalytic efficiency and hold potential for environmental-remediation applications. (C) 2014 Elsevier B.V. All rights reserved.