Mullard Limited was a British manufacturer of electronic components. The Mullard Radio Valve Co. Ltd. of Southfields, London, was founded in 1920 by Captain Stanley R. Mullard, who had previously designed valves for the Admiralty before becoming managing director of the Z Electric Lamp Co. The company soon moved to Hammersmith, London and then in 1923 to Balham, London. At the same time, in order to meet the technical demands of the newly formed BBC, Mullard formed a partnership with the Dutch manufacturer Philips. The vacuum tubes (valves) produced in this period were named with the prefix PM, for Philips-Mullard, beginning with the PM3 and PM4 in 1926. Mullard finally sold all its shares to Philips in 1927. In 1928 the company introduced the first pentode valve to the British market. In the late 1930s Mullard opened a new plant in Blackburn, Lancashire.

By 1949 Mullard had produced a number of television sets, such as the MTS-521 and MTS-684. In 1951 Mullard was producing the LSD series of photographic flash tubes.

The first transistors produced by Mullard were the OC50 and OC51 point-contact types, which were not widely used. In 1953 Mullard moved to junction transistors, beginning with the plastic-cased OC10 series. These were followed by the glass-encapsulated OC70 series, which were produced in large numbers and copied by other companies, such as Valvo (another Philips subsidiary), Intermetall and Siemens in Germany, and Amperex in the USA.

In 1957 Philips-Mullard helped to set up the Mullard Radio Astronomy Observatory (MRAO) at the University of Cambridge. In 1964 the company produced a prototype electronic desk calculator as a technology demonstrator for its transistors and cold cathode indicator tubes. In 1966 the Mullard Space Science Laboratory (MSSL) was opened near Dorking, Surrey as part of University College, London. The Royal Society Mullard Award for young scientists and engineers was set up in 1967. Philips continued to use the brand name "Mullard" in the UK until 1988.