Princeton Nathan Lyman (November 20, 1935 – August 24, 2018) was a diplomat and former United States Ambassador to Nigeria (1986–89) and South Africa (1992–95), and former Assistant Secretary of State for International Organization Affairs (1996–98). He was a member of the American Academy of Diplomacy and the Aspen Institute, and was Adjunct Senior Fellow for Africa Policy Studies with the Council on Foreign Relations. Lyman had a bachelor's degree from the University of California, Berkeley and a Ph.D. from Harvard University.