Louis Joseph Troost (17 October 1825, Paris – 30 September 1911) was a French chemist.

In 1848, he began his studies at the École Normale Supérieure in Paris, where from 1851 he worked as an assistant chemist.

After serving as chair of chemistry at the Lycée Bonaparte, he became a lecturer at the École Normale Supérieure (from 1868).

In addition, he performed significant studies of lithium salts, and with Paul Hautefeuille, he conducted research on the solubility of gases in metals.

[1] Troost was the author of Traité élémentaire de chimie (1847; 24th edition, 1948) that became a standard textbook for successive generations of students.