I. G. Farbenindustrie AG, commonly known as IG Farben, was a German chemical and pharmaceutical conglomerate. It was formed on December 2, 1925 from a merger of six chemical companies: Agfa, BASF, Bayer, Griesheim-Elektron, Hoechst, and Weiler-ter-Meer. It was seized by the Allies after World War II and split into its constituent companies; parts in East Germany were nationalized.