Single crystalline Pt nanowires about 2 nm in diameter with high-aspect ratios are successfully formed over the entire area of glass substrates by utilising lyotropic liquid crystals (LLC) containing cationic surfactants and Pt species. After the LLC films are coated on the substrates by spin-coating, the Pt species are reduced in the presence of the LLC films with an aqueous solution of sodium borohydride. Each Pt nanowire, which is well adhered to the substrate surface, is single crystalline because the nanowires are deposited in LLC films consisting of cationic surfactants acting as a capping agent. In this article, we propose a new role for LLC coated on substrates that provides a reaction field near the surface of substrates and contributes to the anisotropic growth of Pt nanowires.