Nicolas Lenglet Du Fresnoy (5 October 1674 – 16 January 1755) was a French scholar, historian, geographer, philosopher, and bibliographer of alchemy.

In 1705, Jean-Baptiste Colbert de Torcy appointed him Secretary for Latin and French languages to the Elector of Cologne, who lived in Lille.

His love of independence and opposition to royal censors earned him, under Louis XV, five periods of imprisonment in the Bastille, once in the Strasbourg citadel [fr] another time in the Château de Vincennes.

Lenglet, whose books contain treasures of erudition, was interested both in literary criticism as in hermetic philosophy, history, and geography.

In 1681, Géraud de Cordemoy published an anti-protestantist book, the conférence entre Luther et le diable au sujet de la messe with his commentaries,[1] republished and widely distributed in 1875 by Isidore Liseux with commentaries by Nicolas Lenglet Du Fresnoy.