Langlès was born in 1763 in Pérennes, a section of the commune of Welles-Pérennes in the department of the Oise. His youthful efforts to obtain a military position were unsuccessful. Instead, he went to Paris where he enrolled at the Collège de France, studying Arabic and Persian.
Along with Antoine Léonard de Chézy (1773–1832), Jean-François Champollion (1790–1832) and Jean-Pierre Abel-Rémusat (1788–1832), Langlès was a pupil and protégé of Silvestre de Sacy (1758–1838). Langlès close links with the Collège de France were enhanced by Baron de Sacy's support, which also resulted in Chézy becoming the Collège's first Professor of Sanskrit, Rémusat becoming its first Professor of Chinese, and Champollion becoming its first Professor of Egyptology. The faculty encompassed Langlès as the college's Professor of Persian.
In 1795, Langlès became the founder-director the Ecole des langues orientales vivantes in Paris, which is still operating under the revised name of Institut national des langues et civilisations orientales (INALCO).
Langlès was the provisional specialist on India at the Bibliothèque Nationale. France became a center for Indian studies when the accumulated Indian manuscripts languishing in the Bibliothèque Nationale began to be inventoried.