A silicon/silicon-rich nitride hybrid-core waveguide has been proposed and experimentally demonstrated for nonlinear applications to fill the gap between the pure silicon waveguide and the pure silicon nitride waveguide with respect to the nonlinear properties. The hybrid-core waveguide presented here leverages the advantages of the silicon and the silicon-rich nitride waveguide platforms, showing a large nonlinearity γ of 72 ± 5 W−1 m−1 for energy-efficient four-wave mixing wavelength conversion. At the same time, the drawbacks of the material platforms are dramatically mitigated, exhibiting a reduced two-photon absorption coefficient βTPA of 0.023 cm/GW resulting in an increased nonlinear figure-of-merit as large as 21.6. A four-wave-mixing conversion efficiency as large as −5.3 dB has been achieved with the promise to be larger than 0 dB. These findings are strong arguments supporting the silicon/silicon-rich nitride hybrid-core waveguide to be used for energy-efficient nonlinear photonic applications.