Jean-Baptiste Louis Romé de l'Isle (August 26, 1736 – July 3, 1790) was a French mineralogist, considered one of the creators of modern crystallography.
Romé was born in Gray, Haute-Saône, in eastern France. As secretary of a company of artillery in the Carnatic Wars he visited the East Indies, was taken prisoner by the English in 1761, and held in captivity for several years. He was also an alumnus of the Collège Sainte-Barbe in Paris.
Subsequently he became distinguished for his researches on mineralogy and crystallography. He was the author of Essal de Cristallographic (1772), the second edition of which, regarded as his principal work, was published as Cristallographie (3 vols. and atlas, 1783). His formulation of the Law of Constancy of Interfacial Angles built on observations by the geologist Nicolaus Steno.
In 1775, he was elected a foreign member of the Royal Swedish Academy of Sciences. He died in Paris, France on July 3, 1790.