William Willis (1794–1870) was a Portland, Maine lawyer, historian, and politician, and was the partner of William Pitt Fessenden. He was member of the Maine State Senate in 1855 and Mayor of Portland, Maine in 1857, president of the Maine Historical Society (1856–1865), and president of the Maine Central Railroad. In 1864 he was elected a member of the American Antiquarian Society. Bowdoin College, which granted him an honorary degree in 1867, has a small collection of his correspondence, drafts of his writing, and estate information.