We have imaged ˜ 1 deg2 in the V-band in the direction of the Hercules cluster (Abell 2151). The data are used to compute, for the first time, the luminosity function (LF) of galaxies in the cluster down to the dwarf regime (Mlim ˜ -13.85 ). The global LF is well described by a Schechter function (Schechter 1976) with best-fit parameters α = -1.30 ± 0.06 and MV* = -21.25 ± 0.25. The radial dependence of the LF has also been studied, finding that it turns out to be almost constant within the errors even further away than the virial radius. Given the presence of significant substructure within the cluster, we have analized the LFs in different regions. While the LFs of the two subclusters present are consistent with each other and with the global one, the southernmost one exhibits a somewhat steeper faint-end slope.