William Freeman Vilas (July 9, 1840 – August 27, 1908) was a member of the Democratic Party who served in the United States Senate for the state of Wisconsin from 1891 to 1897. He was a prominent Bourbon Democrat. Following the war, Vilas was a Professor of Law at the University of Wisconsin–Madison, and a regent of the University from 1880 to 1885 and 1898 to 1905. Vilas served as a member of the Wisconsin State Assembly in 1885, until he was appointed the Postmaster General between 1885 and 1888, and as Secretary of the Interior from 1888 to 1889, both under President Grover Cleveland.