Westerlund 1 is a unique case of a massive young cluster with at least 11 Wolf-Rayet stars driving strong stellar winds. It is possible that various configurations of these stellar winds (wind-wind interaction, superposition of stellar winds etc.) can convert a fraction of the kinetic energy of the wind into accelerated particles. Observations of spatially extended non-thermal X-ray emission from the highly reddened and nearby stellar cluster Westerlund 1 suggest that indeed stars are able to accelerate at least electrons to TeV energies which then produce X-ray synchrotron emission. We report on the results of H.E.S.S. observations of the Westerlund 1 cluster.