John Sweet Donald (January 12, 1869 – January 10, 1934) was a politician and dentist from the U.S. state of Wisconsin.

Born on a farm near Mount Vernon, Wisconsin, in the town of Springdale, Dane County, Wisconsin,^[1] Donald graduated from Northwestern Business College in 1887, in Madison, Wisconsin.^[1] He then graduated with a bachelor of science degree from Valparaiso University in 1894.^[1] In 1897, Donald received a degree in dentistry from the Chicago College.^[1] He was Wisconsin's nineteenth Secretary of State, serving two terms from January 6, 1913, to January 1, 1917. He was a Republican and served under governors Francis E. McGovern and Emanuel L. Philipp. He resided in Mt. Horeb, Wisconsin, at the time of his election. He served as the Springdale town assessor in 1892. He served as chairman of the Springdale Town Board from 1899 to 1902. Donald served in the Wisconsin State Assembly from 1903 to 1907. He served in the Wisconsin State Senate from 1907 to 1913. He also owned farms in the town of Springdale and taught agriculture at the University of Wisconsin since 1920. Donald died at his home in Madison from a two-year illness.^[1][2][3]

One of his farms, now known as the John Sweet Donald Farmstead, is listed on the National Register of Historic Places.