Pierre-Simon, marquis de Laplace (23 March 1749 – 5 March 1827) is a French mathematician and astronomer whose work is pivotal to the development of mathematical astronomy and statistics.

He summarizes and extends the work of his predecessors in his five-volume Mécanique Céleste (Celestial Mechanics) (1799–1825).

This work translates the geometric study of classical mechanics to one based on calculus, opening up a broader range of problems.

In statistics, the so-called Bayesian interpretation of probability is mainly developed by Laplace.

Laplace formulates Laplace's equation, and pioneers the Laplace transform that appears in many branches of mathematical physics, a field that he takes a leading role in forming.

The Laplacian differential operator, widely used in mathematics, is also named after him.

He restates and develops the nebular hypothesis of the origin of the solar system and is one of the first scientists to postulate the existence of black holes and the notion of gravitational collapse.

Laplace is remembered as one of the greatest scientists of all time.

Sometimes referred to as the French Newton or Newton of France, he possessed a phenomenal natural mathematical faculty superior to that of any of his contemporaries.

Laplace becomes a count of the First French Empire in 1806 and is named a marquis in 1817, after the Bourbon Restoration.