Guillaume Jacques (, born 1979) is a French linguist who specializes in the study of Sino-Tibetan languages: Old Chinese, Tangut, Tibetan, Gyalrongic and Kiranti languages. He also performs research on the Algonquian and Siouan language families and publishes about languages of other families such as Breton. His case studies in historical phonology are set in the framework of panchronic phonology, aiming to formulate generalizations about sound change that are independent of any particular language or language group.