Jacques Lelong (occasionally Jacobus Longus; 19 April 1665 – 13 August 1721) was a French bibliographer born in Paris.
[1] He was a priest of the Oratory, and was librarian to the establishment of the Order in Paris, where he spent his life in seclusion.
He first published a Bibliotheca Sacra (1709), an index of all the editions of the Bible, then a Bibliothèque historique de la France (1719), a volume of considerable size, containing 17,487 items to which Lelong sometimes appends useful notes.
He vainly hoped that his friend and successor Father Desmolets would continue it; but it was resumed by Charles-Marie Fevret de Fontette [fr], a councillor of the parlement of Dijon, who spent fifteen years of his life and a great deal of money in rewriting the Bibliothèque historique.
In this new edition the Bibliothèque historique is a work of reference of the highest order; it is still of great value.