Jean-Etienne Guettard (September 22, 1715 - January 7, 1786) was a French naturalist and mineralogist.

Guettard was born in Etampes . In boyhood, he gained a knowledge of plants from his grandfather, who was an apothecary, and later he qualified as a doctor in medicine. Pursuing the study of botany in various parts of France and other countries, he began to take notice of the relation between the distribution of plants and the soils and subsoils . In this way his attention came to be directed to minerals and rocks. In 1746, he communicated to the Academy of Sciences in Paris a memoir on the distribution of minerals and rocks, and this was accompanied by a map on which he had recorded his observations. He thus, as remarked by W. D. Conybeare, first carried into execution the idea, proposed by of his journeys he made a large collection of fossils and figured many of them, but he had no clear ideas about the sequence of strata. He made observations also on the degradation of mountains by rain, rivers and sea; and he was the first to ascertain the existence of former volcanoes in the district of Auvergne.

He died in Paris.