William Jayne (October 8, 1826 - March 20, 1916) was a Delegate from Dakota Territory to the United States House of Representatives. He was born in Springfield, Illinois, and graduated in medicine from the University of Missouri at Columbia in 1849. He began his practice in Springfield, and became mayor of Springfield, and then a member of the State Senate in 1860, but resigned in 1861 to accept the appointment of Governor of Dakota Territory. He served from 1861-1863, then as a Delegate to the House from March 4, 1863 to June 17, 1864.

Jayne returned to Springfield and continued the practice of medicine. He served three terms as mayor of Springfield, and as pension agent. In 1873 he resumed the practice of medicine. He died in Springfield and is intered in Oak Ridge Cemetery in Springfield.