major British corporation that was founded in 1926 as Imperial Chemical Industries Ltd. to amalgamate four major British chemical companies: Brunner, Mond & Co. Ltd., Nobel Industries Ltd., United Alkali Company Ltd., and British Dyestuffs Corporation Ltd. Between World Wars I and II, ICI was a major competitor of Germany's IG Farben, the cartel formed in 1925 (and dissolved by the Allies after World War II). By the late 1970s, ICI ranked below all three successors to IG Farben (Hoechst, BASF, and Bayer corporations) in terms of sales but was still the largest chemical concern in the United Kingdom. ICI's headquarters are in London.

ICI's constituent companies in 1926 produced chemicals, dyes, explosives, fertilizers, fibres, nonferrous metals, and paints, and the group went on to produce a wider range of chemicals, paints, pharmaceuticals, synthetic fibres (especially polyesters and nylon), and plastics. In 1993 ICI split off its drug, pesticide, and specialty chemical concerns into a new corporation named Zeneca Group PLC. The parent company continued to produce industrial polymers and other chemicals, paints, and explosives. In 1997 ICI bought the specialty chemicals business of Unilever.