Imperial Chemical Industries (ICI) was a British chemical company. It was, for much of its history, the largest manufacturer in Britain. It was formed by the merger of four leading British chemical companies in 1926. Its headquarters were at Millbank in London. ICI was a constituent of the FT 30 and later the FTSE 100 indices.

The chemical industry comprises the companies and other organizations that develop and produce industrial, specialty and other chemicals. Central to the modern world economy, it converts raw materials into commodity chemicals for industrial and consumer products. It includes industries for petrochemicals such as polymers for plastics and synthetic fibers; inorganic chemicals such as acids and alkalis; agricultural chemicals such as fertilizers, pesticides and herbicides; and other categories such as industrial gases, speciality chemicals and pharmaceuticals.