Lucien Cayeux

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| name = Lucien Cayeux

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| birth_date = {{Birth date|1864|3|26|df=y}}

| birth_place = France

| death_date = {{Death date and age|1944|11|1|1864|3|26|df=y}}

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| fields = Geology

| workplaces = Collège de France

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| known_for = Pioneering petrography of sedimentary rocks

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| awards = Member, French Academy of Sciences

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Lucien Cayeux (26 March 1864–1 November 1944) was a French sedimentary petrographer.

In 1902, he 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.

The wrinkle ridge Dorsum Cayeux on the moon is named after him.