Two-dimensional (2D) and three-dimensional (3D) magnetic cobalt nanowire thin films with tunable 3-10 nm wire diameters have been electrodeposited using mesoporous silica templates containing 2D hexagonal or 3D cubic pore channels. As compared to bulk cobalt films, the cobalt nanowire thin films exhibit enhanced coercivities and controllable magnetic anisotropy through tuning of the mesostructure and dimension of the nanowires. Such novel magnetic nanowire thin films may provide a new platform for high-density information storage applications.