Josiah Butler Williams (December 16, 1810 Middletown, Middlesex County, Connecticut – September 26, 1883 Ithaca, Tompkins County, New York) was an American businessman, banker and politician from New York.
He was the son of Josiah Williams (1768–1842) and Charity (Shaler) Williams (1775–1865). He married Mary Huggeford Hardy (1824–1911), and they had 12 children, among them geologist Henry Shaler Williams (1847–1918).
He was a Whig member of the New York State Senate (25th D.) from 1852 to 1855, sitting in the 75th, 76th, 77th and 78th New York State Legislatures.
Williams was nominated on the Know Nothing ticket for Canal Commissioner at the New York state election, 1854, but two weeks before the election declined to run. The party managers then substituted Hard Democrat Clark Burnham on the ticket but, due to slow communications, Williams still polled almost 60,000 votes.
He was a presidential elector in 1856, voting for John C. Frémont and William L. Dayton.
He was buried at the Ithaca City Cemetery.
State Senator Timothy S. Williams (1800–1849) was his brother; lumber magnate Henry W. Sage (1814–1897) was his nephew.