National Physical Laboratory (NPL) was founded in 1900 at Bushy House, Teddington, London "for standardising and verifying instruments, for testing materials, and for the determination of physical constants." It is one of the oldest standardising laboratories in the world.

It was originally conceived as an extension of Kew Observatory, which was situated round the corner in Old Deer Park at Richmond, and for the first 18 years of its existence, NPL was under the control of the Royal Society.

Since its establishment, the research work at NPL has included all branches of physics, light, electricity and magnetism, radio communication, engineering, metallurgy, aeronautics and ship design. Many of Britain's most renowned scientists have been involved in work at NPL, including Alan Turing, Louis Essen and Donald Davies.

Some of the most notable achievements carried out at NPL include the invention of the Automatic Computer Engine (ACE), packet switching, radar and the atomic clock.

Their current address is National Physical Laboratory, Hampton Road, Teddington, Middlesex, TW11 0LW.