Résumé
Stellar clusters are potential acceleration sites of very-high-energy (VHE, E> 100GeV) particles since they host supernova remnants (SNRs) and pulsar windnebulae (PWNe). Additionally, in stellar clusters, particles can also beaccelerated e.g. at the boundaries of wind-blown bubbles, in colliding windzones in massive binary systems or in the framework of collective wind orwind/supernova(SN) ejecta scenarios. Motivated by the detection of VHEgamma-ray emission towards Westerlund 2 and assuming similar particleacceleration mechanisms at work, Westerlund 1 is an even more promising targetfor VHE gamma-ray observations given that massive star content and distance aremore favorable for detectable VHE gamma-ray emission compared to Westerlund 2.Here, H.E.S.S. observations of massive stellar clusters in general with specialemphasis on the most massive stellar cluster in the galaxy, Westerlund 1 aresummarized.