Irving Langmuir (31 January 1881 – 16 August 1957) was an American chemist and physicist.

He earned his Ph.D. degree in 1906 under Nobel laureate Walther Nernst in Göttingen, for research done using the "Nernst glower", an electric lamp invented by Nernst. His doctoral thesis was entitled “On the Partial Recombination of Dissolved Gases During Cooling.” Langmuir then taught at Stevens Institute of Technology in Hoboken, New Jersey, until 1909, when he began working at the General Electric research laboratory .
His first major development was the improvement of the diffusion pump, which ultimately led to the invention of the high-vacuum tube.
In 1917, he published a paper on the chemistry of oil films that later became the basis for the award of the 1932 Nobel Prize in chemistry.
He introduced the concept of electron temperature and in 1924 invented the diagnostic method for measuring both temperature and density with an electrostatic probe, now called a Langmuir probe and commonly used in plasma physics.
In 1938, Langmuir's scientific interests began to turn to atmospheric science and meteorology.
In 1953 Langmuir coined the term "pathological science", describing research conducted with accordance to the scientific method, but tainted by unconscious bias or subjective effects.
His house in Schenectady, was designated a National Historic Landmark in 1976.