Low-temperature efficient hydrogenation of CO bonds in various compounds, which is one of the most important processes for producing fuels and chemicals, is of fundamental interest but remains a significant challenge. The primary problem is a lack of heterogeneous catalyst systems that are highly active at ambient or low temperatures. This paper describes an efficient strategy for designing a low-temperature hydrogenation catalyst. Ru nanoparticles supported on reduced graphene oxide (Ru/RGO) show remarkable efficiency for hydrogenation of levulinic acid into γ-valerolactone at temperatures as low as −10 °C. The catalyst is also highly active toward low-temperature hydrogenation of CO bonds in other carbonyl compounds into C–OH bonds, such as furfural, propionaldehyde, 2-pentanone, hydroxyacetone, acetone, acetophenone, cyclohexanone, and benzophenone. X-ray photoelectron spectroscopy and in situ Fourier transform infrared demonstrate that the electron transfer between Ru0 and RGO leads to the formation of an electron-rich state of Ru0 nanoparticles that are highly effective for activating CO bonds.