Two-dimensional lattices of coupled micropillars etched in a planar semiconductor microcavity offer a workbench to engineer the band structure of polaritons. We report experimental studies of honeycomb lattices where the polariton low energy dispersion is analogous to that of electrons in graphene. Using energy resolved photoluminescence we directly observe Dirac cones, around which the dynamics of polaritons is described by the Dirac equation for massless particles. At higher energies, we observe p orbital bands, one of them with the non-dispersive character of a flat band. The realization of this structure which holds massless, massive and infinitely-massive particles opens the route towards studies of the interplay of dispersion, interactions and frustration in a novel and controlled environment.