French explorer, surveyor and naturalist from Draguignan, Provence, who travelled in South America during two voyages (1828-1832, 1834-1842) and wrote a flora of Chile. During the first expedition the Chilean government commissioned him to take astronomical observations and prepare a scientific survey of the republic. He was appointed Professor of Physics and Chemistry at Santiago College (1828-1842). Gay was elected a member of the French Academy of Sciences and travelled on their behalf to Russia (1856-1858) and to the United States (1858-1860) to study their mining systems. The genus Gayophytum Juss. in the Onagraceae was named in his honour, based on his Chilean collections.