We synthesize vertically oriented core-shell nanowires with substoichiometric MoO(3) cores of ∼20-50 nm and conformal MoS(2) shells of ∼2-5 nm. The core-shell architecture, produced by low-temperature sulfidization, is designed to utilize the best properties of each component material while mitigating their deficiencies. The substoichiometric MoO(3) core provides a high aspect ratio foundation and enables facile charge transport, while the conformal MoS(2) shell provides excellent catalytic activity and protection against corrosion in strong acids.