William Alfred Preston (July 26, 1848 – August 22, 1944) was a Canadian politician, who served as a Member of Provincial Parliament in Ontario from 1907 to 1911.
William Preston was born July 26, 1848, in Bethany, Manvers Township, Durham County, Ontario.
He was the son of Major Isaac Preston Jr. (New Amsterdam, New York; Amherst Island, ON, Manvers Township, ON, and Vancouver, BC) and Mary Anne Woodside (Bellin, County Londonderry, Ireland, and Amherst Island, ON.)
After James Arthur Mathieu won the Conservative nomination in 1911, Preston chose to run as a Liberal and was defeated.
He, along with others, had applied for a charter to form the Rainy Lake Pulp and Paper Company in Fort Frances.