We report vertically illuminated, resonant cavity enhanced, graphene–Si Schottky photodetectors (PDs) operating at 1550 nm. These exploit internal photoemission at the graphene–Si interface. To obtain spectral selectivity and enhance responsivity, the PDs are integrated with an optical cavity, resulting in multiple reflections at resonance, and enhanced absorption in graphene. We get a wavelength-dependent photoresponse with external (internal) responsivity ∼20 mA/W (0.25A/W). The spectral selectivity may be further tuned by varying the cavity resonant wavelength. Our devices pave the way for developing high responsivity hybrid graphene–Si free-space illuminated PDs for optical communications, coherence optical tomography, and light-radars.