William Durie Lyon (; June 5, 1825 – October 18, 1893) was a merchant and political figure in Ontario, Canada.
Lyon was a Liberal member of the Legislative Assembly of Ontario who was elected in 1875 to represent the riding of Halton.
In 1879, he became the de facto governor of the District of Rainy River, holding executive, judicial and magisterial power over the new settlements situated west of Ontario.