Nils Abraham Langlet (9 July 1868 – 30 March 1936; known by his second given name) was a Swedish chemist.
Langlet was born in Södertälje. From 1886 to 1896, he studied chemistry under Per Teodor Cleve at Uppsala University, where he obtained a doctorate in 1896, and was made docent in the same year. In 1899, he became lecturer in Chemistry and Chemical Technology at the Chalmers University of Technology in Gothenburg, where he received a professorship in the same field in 1911. From 1926, when his professorship was divided, he was professor of Organic Chemistry.
In 1895, while working with Cleve in Uppsala, he made the independent discovery of the element helium (in the same year discovered by William Ramsay) in the mineral cleveite. Langlet was the first to correctly define its atomic weight. He died in Gothenburg.