Sanofi S.A. is a French multinational pharmaceutical company headquartered in Gentilly, France, as of 2013 the world's fifth-largest by prescription sales. The company was formed as Sanofi-Aventis in 2004 by the merger of Aventis and Sanofi-Synthélabo, which were each the product of several previous mergers. It changed its name to Sanofi in May 2011. The company is a component of the Euro Stoxx 50 stock market index.