Saint-Genis-Pouilly is a commune in the Ain department in eastern France.
It is located in the Pays de Gex, at the foot of the Jura. Bordering the Swiss frontier, it is part of the cross-border area of Geneva. Because of its population, it is one of the ten most important towns in the department of Ain. Its inhabitants are known as Saint-genésiens.
A large portion of CERN, the European laboratory for particle physics, is located in the territory of Saint-Genis-Pouilly. CERN is one of the top locations in the world for fundamental research and it is the presence of CERN that has been responsible for the development of the community since the middle of the 1960s.