Louis Trolle Hjelmslev (Danish: ['j?l?msle??]; 3 October 1899 – 30 May 1965) was a Danish linguist whose ideas formed the basis of the Copenhagen School of linguistics.
Born into an academic family (his father was the mathematician Johannes Hjelmslev), Hjelmslev studied comparative linguistics in Copenhagen, Prague and Paris (with Antoine Meillet and Joseph Vendryes, among others).
In 1931, he founded the Cercle Linguistique de Copenhague.
Together with Hans Jørgen Uldall he developed a structural theory of language which he called glossematics, which developed the semiotic theory of Ferdinand de Saussure.
Glossematics as a theory of language is characterized by a high degree of formalism, it is interested only in describing the formal characteristics of language, and has a high degree of logical rigour.
The theory never became widely influential, but has been adopted by post-structuralist philosophers as a possible alternative to the dominant Saussurean linguistic paradigm.