William A. Jayne (October 8, 1826 – March 20, 1916) was an American politician and physician. He served as Governor of the Dakota Territory and as the territory's delegate to the United States House of Representatives during the American Civil War. Jayne then returned to Springfield and continued the practice of medicine. He was appointed U.S. Pension Agent in 1869 for four years and served three terms as mayor of Springfield beginning in 1876. He also served as Director and Vice President of the First National Bank of Springfield. He resumed the practice of medicine in 1873.