Langmuir, who was born in Brooklyn, New York, studied metallurgical engineering at the Columbia School of Mines, New York. He then went on to do postgraduate work under Walther Nernst at Göttingen, where he obtained his PhD in 1906. On his return to America he taught for a short time at the Stevens Institute of Technology, New Jersey, before joining the research laboratory of the General Electric Company (GEC), Schenectady, New York, (1909) where he remained until his retirement in 1950.

Langmuir was an extremely original and productive industrial physical chemist. In 1913 he achieved a major breakthrough in the design of electric light bulbs. The vacuum tubes (tungsten bulbs) then in use contained an incandescent tungsten wire that tended to break and also deposited a black film inside the bulb. Most research to rectify this was concentrating on improving the quality of the vacuum in the bulb. Langmuir saw that the same effect could be obtained more cheaply and efficiently by filling the bulb with an inert gas. After much experimentation he found that a mixture of nitrogen and argon did not attack the tungsten filament and eliminated the oxidation on the bulb.

In 1919 Langmuir tried to develop the theory of the electron structure of the atom published by Gilbert Lewis in 1916. Lewis had only dealt with the first two rows of the periodic table and Langmuir tried to extend it. He proposed that electrons tend to surround the nucleus in successive layers of 2, 8, 8, 18, 18, and 32 electrons respectively. Then using similar arguments to those of Lewis he went on to try and explain the basic facts of chemical combination. It was not until after the development of quantum theory in the 1920s that a definitive account could be provided by Linus Pauling.

Langmuir also developed a vacuum pump, constructed a hydrogen blowtorch (1927) for welding metals at high temperatures, and worked on the production of artificial rain with Vincent Schaefer in 1947. In his research career he conducted a prolonged investigation into the chemistry of surfaces, tackling such problems as how and why certain substances spread on water and how gases interact with metal surfaces. Langmuir introduced the idea of adsorption of a single layer of atoms (a monolayer) on a surface and the theory that surface reactions (as in heterogeneous catalysis) take place between adsorbed molecules or atoms. The Langmuir isotherm is an expression relating the amount of adsorption on a surface with the gas pressure (at constant temperature). He was awarded the Nobel Prize for chemistry in 1932 for his research into surface reactions.