The Atlas was one of the world's first supercomputers, in use from 1962 (when it was claimed to be the most powerful computer in the world) to 1972. Atlas's capacity promoted the saying that when it went offline, half of the United Kingdom's computer capacity was lost. It is notable for being the first machine with virtual memory (at that time referred to as "one-level store") using paging techniques; this approach quickly spread, and is now ubiquitous.

Atlas was a second-generation computer, using discrete germanium transistors. Atlas was created in a joint development effort among the University of Manchester, Ferranti and Plessey. Two other Atlas machines were built: one for BP and the University of London, and one for the Atlas Computer Laboratory at Chilton near Oxford.

A derivative system was built by Ferranti for the University of Cambridge. Called the Titan, or Atlas 2, it had a different memory organisation and ran a time-sharing operating system developed by Cambridge University Computer Laboratory. Two further Atlas 2s were delivered: one to the CAD Centre in Cambridge (later called CADCentre, then AVEVA), and the other to the Atomic Weapons Research Establishment (AWRE), Aldermaston.

The University of Manchester's Atlas was decommissioned in 1971. The final Atlas, the CADCentre machine, was switched off in late 1976. Parts of the Chilton Atlas are preserved by National Museums Scotland in Edinburgh; the main console itself was rediscovered in July 2014 and is at Rutherford Appleton Laboratory in Chilton, near Oxford.

Through 1956 there was a growing awareness that the UK was falling behind the US in computer development. In April, B.W. Pollard of Ferranti told a computer conference that "there is in this country a range of medium-speed computers, and the only two machines which are really fast are the Cambridge EDSAC 2 and the Manchester Mark 2, although both are still very slow compared with the fastest American machines." This was followed by similar concerns expressed in May report to the Department of Scientific and Industrial Research Advisory Committee on High Speed Calculating Machines, better known as the Brunt Committee.

Through this period, Tom Kilburn's team at the University of Manchester had been experimenting with transistor-based systems, building two small machines to test various techniques. This was clearly the way forward, and in the autumn of 1956, Kilburn began canvassing possible customers on what features they would want in a new transistor-based machine. Most commercial customers pointed out the need to support a wide variety of peripheral devices, while the Atomic Energy Authority suggested a machine able to perform an instruction every microsecond, or as it would be known today, 1 MIPS of performance. This later request led to the name of the prospective design, MUSE, for microsecond engine.

The need to support many peripherals and the need to run fast are naturally at odds. A program that processes data from a card reader, for instance, will spend the vast majority of its time waiting for the reader to send in the next bit of data. To support these devices while still making efficient use of the central processing unit (CPU), the new system would need to have additional memory to buffer data and have an operating system that could coordinate the flow of data around the system.

When the Brunt Committee heard of new and much faster US designs, the Univac LARC and IBM STRETCH, they were able to gain the attention of the National Research Development Corporation (NRDC), responsible for moving technologies from war-era research groups into the market. Over the next eighteen months, they held numerous meetings with prospective customers, engineering teams at Ferranti and EMI, and design teams at Manchester and the Royal Radar Establishment.