Alexandre-Théophile Vandermonde (28 February 1735 -1 January 1796) was a French musician and chemist who worked with Bezout and Lavoisier; his name is now principally associated with determinant theory in mathematics. He was born in Paris, and died there.

He was a violinist, and became engaged with mathematics only around 1770. In Mémoire sur la résolution des équations (1771) he reported on symmetric functions and solution of cyclotomic polynomials; this paper anticipated later Galois theory. In Remarques sur des problèmes de situation (1771) he studied knight's tours. Mémoire sur des irrationnelles de différens ordres avec une application au cercle (1772) was on combinatorics, and Mémoire sur l'élimination (1772) on the foundations of determinant theory. These papers were presented to the Académie des Sciences, and constitute all his published mathematical work. The Vandermonde determinant does not make an explicit appearance.

A special class of matrices, the Vandermonde matrices are named after him, as is an elementary fact of combinatorics, Vandermonde's identity.