Stéphane Udry (born 1961 in Sion, Switzerland) is an astronomer at the Geneva Observatory in Switzerland, whose current work is primarily the search for extra-solar planets. He and his team, in 2007, discovered a possibly terrestrial planet in the habitable zone of the red dwarf star Gliese 581, approximately 20 light years away in the constellation Libra. He also led the observational team that discovered HD 85512 b, another most promisingly habitable exoplanet.