Constantin I. Istrati (7 September 1850 – 17 January 1919) was a Romanian chemist and physician. He was president of the Romanian Academy between 1913 and 1916. He was born in 1850 in Roman, Moldavia (now in Neamț County, Romania). He studied at the Academia Mihăileană in Iași, after which he went to Bucharest to study at the University of Medicine and Pharmacy, graduating in 1869, and obtaining his M.D. in 1877. After collaborating with Carol Davila, Istrati pursued his studies for three years at the University of Paris, where he obtained in 1885 a Ph.D. in Chemistry under the direction of Charles Adolphe Wurtz and Charles Friedel, with thesis On colored ethylbenzene and some observations about boiling points in the aromatic series.