Jonas Fay (January 17, 1737 – March 6, 1818) was a military and political leader of Vermont during its period as an independent republic, and during the early years of its statehood. Born in Massachusetts, he served in the militia during the French and Indian War, studied medicine, and became a physician. His father moved to Vermont during its formative years, and Jonas Fay moved with him. Fay was active in the Green Mountain Boys and their resistance to New York's efforts to assume jurisdiction over Vermont. In 1775, he served as physician for the contingent of Green Mountain Boys that captured Fort Ticonderoga.