Imperial Chemical Industries (ICI) was formed in 1926 by the merger of four of the largest chemical companies in Britain - Nobel Industries, Brunner Mond, British Dyestuffs and United Alkali. Nobel Industries had been founded by Alfred Nobel, inventor of dynamite and instigator of the Nobel Prizes. The reason for the merger was to create a company big enough to respond to competition from Europe. In its first year of operation, ICI employed 33,000 people and made sales of £27 million.

ICI's best known product is probably Dulux paint, which was introduced in 1953, and the Dulux dog is one of the most easily recognizable characters in British advertising. The breed, the Old English Sheepdog, was fairly uncommon when the Dulux dog first appeared in the 1960s, but due to the influence of the adverts soon gained greatly in popularity.

ICI is responsible for over 33,000 patented inventions. Their first great invention was polyethylene, which was discovered in a laboratory accident. Other notable inventions include Perspex, Paludrine (an anti-malaria drug), and the weedkiller Paraquat.

In the 1990s the company was split into two. A new company, Zeneca, took on some areas of business, leaving ICI to concentrate on paints and chemicals. ICI Paints are still based in Slough.