Lucien Cayeux (March 16, 1864–November 1, 1944) was a French sedimentary petrographer.
In 1902 joined the l'Ecole des Mines and become a professor of geology. In 1912 he was named as professor of geology at the Collège de France. He was admitted to the Académie des Sciences in 1928.
He is noted for his study of sediments with the polarizing microscope, and was one of the pioneers in this field.
- "Études des Gites Minéraux de la France", 1906.
- "Les Minerais de Fer Oolithiques de France", 1909.
- "Introduction à l'étude Pétrographique des Roches Sédimentaires", 1916.
- "Les Roches Sédimentaires de France", 1929.
- "Les Phosphates de Chaux Sédimentaire de France", 1941.
- "Causes Anciennes et Causes Actuelles en Géologie", 1941.
He also published a number of scientific papers.