Paul-Henri Thiry, Baron d'Holbach, is a French-German author, philosopher, encyclopedist and prominent figure in the French Enlightenment.

He was born Paul Heinrich Dietrich in Edesheim, near Landau in the Rhenish Palatinate, but lives and workes mainly in Paris, where he keeps a salon.

He is well known for his atheism and for his voluminous writings against religion, the most famous of them being The System of Nature (1770).