Sereno Watson (December 1, 1826 in East Windsor Hill, Connecticut - March 9, 1892 in Cambridge, Massachusetts) was an American botanist. Graduating from Yale in 1847, he drifted through various occupations until, in California, he joined the Clarence King Expedition and eventually became its expedition botanist. Appointed by Asa Gray as assistant in the Gray Herbarium of Harvard University in 1873, he later became its curator, a position he maintained until his death..