EG&G, formally known as Edgerton, Germeshausen, and Grier, Inc., was an American national defense contractor and provider of management and technical services. The company was involved in contracting services to the United States government during World War II and conducted the research and development on the nuclear weapons during the Cold war era (from 1948 and onward) together with the American national laboratories in Nevada Test Site.

It had close involvement with some of the government's most sensitive technologies, including providing support to stealth development led by the Lockheed Martin, also in Nevada.

In 1931, Massachusetts Institute of Technology (MIT) professor Harold Edgerton, a pioneer of high-speed photography, partnered with his graduate student Kenneth Germeshausen to found a small technical consulting firm. The two were joined by fellow MIT graduate student Herbert E. Grier in 1934. Bernard "Barney" O'Keefe became the fourth member of their fledgling technology group.

The group's high-speed photography was used to image and radiography the implosion-type tests during the Manhattan Project in 1945. The same skills in precisely timed high-power electrical pulses also formed a key enabling technology for nuclear weapon triggers. After the war, the group continued their association with the burgeoning military nuclear effort and formally incorporated Edgerton, Germeshausen, and Grier, Inc. in 1947.

During the 1950s and 1960s, the EG&G was involved in nuclear tests as a prime contractor for the U.S. Atomic Energy Commission, later the U.S. Department of Energy (DOE). During that time, the company extensively managed and operated the Nevada Test Site (NTS) for researching and developing the nuclear weapons together with American nuclear physics laboratories (LLNL, LANL, and SNL), as well developing the remote sensing technologies at the Nellis Air Force Base in Nevada. The EG&G had shared operations responsibility for the NTS with Livermore, Raytheon Services Nevada, Reynolds Electrical and Engineering Company (REECO), SOC LLC, Los Alamos Labs, Sandia Labs, and others.

Subsequently, the EG&G expanded its range of services, providing facilities management, technical services, security, and fighter pilot training for the U.S. military and other government departments. EG&G built a variety of sensing, detection and imaging products including night vision equipment, sensors for detection of nuclear material and chemical and biological weapons agents, and a variety of acoustic sensors. The company also supplied microwave and electronic components to the government, security systems, and systems for electronic warfare and mine countermeasures.

During the 1970s and 1980s, the company, then led by O'Keefe, diversified by acquisition into the fields of paper making, instrumentation for scientific, marine, environmental and geophysical users, automotive testing, fans and blowers, frequency control devices and other components including BBD and CCD technology via their Reticon division. In early to late 1980s, the EG&G had supported the work of the Skunk Works in developing the stealth technology. In the late 1980s and early 1990s most of these divisions were sold, and on 28 May 1999, the non-government side of EG&G Inc.; formerly NYSE: EGG; purchased the Analytical Instruments Division of PerkinElmer for US$425 million (equivalent to $802.2 million in 2024), also assuming the PerkinElmer name (NYSE: PKI).

At the time EG&G was based in Wellesley, Massachusetts, and made products for diverse industries including automotive, medical, aerospace and photography. At least in 1988, there was either a subsidiary or internal department of EG&G dubbed EG & G Biomolecular that produced the Acugen 402 DNA sequencer, the first (and perhaps only) commercially available automated DNA sequencer that used slab gel electrophoresis and radioactive Sanger sequencing.