Context : Aims : The BL Lac object RGB J0152 + 017 ( z = 0.080 ) was predicted to be a very high-energy ( VHE ; > 100 GeV ) \gamma -ray source , due to its high X-ray and radio fluxes . Our aim is to understand the radiative processes by investigating the observed emission and its production mechanism using the High Energy Stereoscopic System ( H.E.S.S . ) experiment . Methods : We report recent observations of the BL Lac source RGB J0152 + 017 made in late October and November 2007 with the H.E.S.S . array consisting of four imaging atmospheric Cherenkov telescopes . Contemporaneous observations were made in X-rays by the Swift and RXTE satellites , in the optical band with the ATOM telescope , and in the radio band with the Nançay Radio Telescope . Results : A signal of 173 \gamma -ray photons corresponding to a statistical significance of 6.6 \sigma was found in the data . The energy spectrum of the source can be described by a powerlaw with a spectral index of \Gamma = 2.95 \pm 0.36 _ { \mathrm { stat } } \pm 0.20 _ { \mathrm { syst } } . The integral flux above 300 GeV corresponds to \sim 2 % of the flux of the Crab nebula . The source spectral energy distribution ( SED ) can be described using a two-component non-thermal synchrotron self-Compton ( SSC ) leptonic model , except in the optical band , which is dominated by a thermal host galaxy component . The parameters that are found are very close to those found in similar SSC studies in TeV blazars . Conclusions : RGB J0152 + 017 is discovered as a source of VHE \gamma -rays by H.E.S.S . The location of its synchrotron peak , as derived from the SED in Swift data , allows clear classification as a high-frequency-peaked BL Lac ( HBL ) .