Jay Harold Jasanoff ( or ) is an American linguist and Indo-Europeanist, best known for his h₂e-conjugation theory of the Proto-Indo-European verbs. He teaches Indo-European linguistics and historical linguistics at Harvard University.
Jasanoff, of Eastern Europe Jewish background, was born in New York City. He received both his bachelor's degree (in 1963) and his Ph.D. (in 1968) from Harvard. After working for one year as an assistant professor at the University of California, Berkeley, he returned to Harvard to teach as an assistant professor and, later, associate professor from 1970 to 1978. He then moved to Ithaca, New York, to teach at Cornell University, where he was promoted to full professor in linguistics. He taught at Cornell for twenty years, including a number of years as the department chair. Since 1998 he has been the Diebold Professor of Indo-European Linguistics and Philology at Harvard, and was the department chair from 1999 to 2008.
In his research, he has examined, in addition to the Indo-European verb, such issues as the origin of the Balto-Slavic pitch accent and the internal reconstruction of the earliest stages of the Proto-Indo-European language.
His wife, Sheila Jasanoff, is a professor at the Harvard Kennedy School. His daughter, Maya Jasanoff, is a professor in the Department of History at Harvard, and his son, Alan Jasanoff, is a neuroscientist at MIT.