Elliott Brothers (London) Ltd was an early computer company of the 1950s and 1960s in the United Kingdom. It traced its descent from a firm of instrument makers founded by William Elliott in London around 1804. The research laboratories were originally set up in 1946 at Borehamwood and the first Elliott 152 computer appeared in 1950.

In its day the company was very influential. The computer scientist Bobby Hersom was an employee from 1953 to 1954, and Sir Tony Hoare was an employee there from August 1960 to 1968. He wrote an ALGOL 60 compiler for the Elliott 803. He also worked on an operating system for the new Elliott 503 Mark II computer. The founder of the UK's first software house, Dina St Johnston, had her first programming job there from 1953 to 1958, and John Lansdown pioneered the use of computers as an aid to planning on an Elliott 803 computer in 1963. In 1966 the company established an integrated circuit design and manufacturing facility in Glenrothes, Scotland, followed by a metal–oxide semiconductor (MOS) research laboratory.

In 1967, Elliott Automation was merged into the English Electric company and in 1968 the computer part of the company became part of International Computers Limited (ICL).

William Elliott was born in either 1780 or 1781 and apprenticed to the instrument maker William Blackwell in 1795. In 1804, Elliott began his own company to make drawing instruments, scales, and scientific instruments. In 1850, his two sons Charles and Fredrick joined his business. The company prospered, and manufactured a range of surveying, navigational, and other instruments. William Elliott died in 1853. In the 1850s the company began manufacturing electrical instruments, which were used by researchers such as James Clerk Maxwell and others. Charles Elliott retired in 1865, and when Frederick died in 1873 he left the business to his wife Susan.

In 1876, the company expanded to a new factory to manufacture telegraph equipment and instruments for the British Admiralty. There was increased demand for electrical switchboards for the growing electric power industry. Susan Elliott became partners with Willoughby Smith, who had significant expertise in telegraphic instruments; she was the last Elliott family member associated with the company when she died in 1880. Smith in turn brought his sons in to manage the company operations.

In 1893, the instrument making company Theilers joined Elliotts, with W. O. Smith and G. K. E. Elphinstone as managers. Elphinstone had useful connections with the British Navy. He was knighted for his contributions at Elliotts during World War I, with developments in gunnery instruments for the Navy.

In 1898, the company moved out of London to a new site in Lewisham, then located in Kent. One of the main products at this site was naval gunnery tables, which were mechanical analog computers, which were manufactured until after World War II. Aircraft instruments became an important product line with the development of heavier than air flight; instruments such as tachometers and altimeters were vital in aviation. In 1916, the company changed its name to Elliott Brothers (London), Limited. In 1920, Siemens Brothers started purchasing shares of the company.

The end of Admiralty contracts after the war severely affected Elliott Brothers, which had not been involved in radar and electronics technology during the war. Siemens Brothers had sold their interest in the company, and a new director, Leon Bagrit, was instrumental in rebuilding and redirecting the firm into new areas.