The quantum-well states (QWSs) associated with electron confinement on the nanometer scale have attracted considerable interest due to their importance in low-dimensional physics and in magnetic/electronic device applications. To study QWSs in noble metal systmes, we grew atomically uniform Au films on Ag(111) surface. The Au QWSs are observed by using Angle-resolved photoemission spectroscopy (ARPES). The Au QWSs hybridize with the Ag states and thus, show an energy dependence on the thickness of the supporting Ag film and the thickness of the Au overlayer. Furthermore, a sandwich structure of Ag/Au/Ag is fabricated with different thicknesses of constituent layers. The Au d-states, though buried under the Ag overlayers, are still observable through hybridization with the Ag states. In this heterostructure, Au and Ag orbitals hybridize and form hybrid QWSs of which the charge density spread across the whole film. Interestingly, the hybrid quantum well states with Au d-orbitals possess a large effective mass as a consequence of partially localized nature of d-states. Detailed first-principles simulations are performed to illustrate the orbital components of hybrid QWSs and provide an insight into the band dispersion of hybrid states.