The System of Nature or, the Laws of the Moral and Physical World is a 1770 work of philosophy by Paul-Henri Thiry, Baron d'Holbach.

Paul-Henri Thiry, Baron d'Holbach, known as d'Holbach, was a Franco-German philosopher, encyclopedist and writer, who was a prominent figure in the French Enlightenment. He was born Paul Heinrich Dietrich in Edesheim, near Landau in the Rhenish Palatinate, but lived and worked mainly in Paris, where he kept a salon. He helped in the dissemination of "Protestant and especially German thought", particularly in the field of the sciences, but was best known for his atheism and for his voluminous writings against religion, the most famous of them being The System of Nature (1770) and The Universal Morality (1776).