Justin A. Smith (March 20, 1818 Whitehall, Washington County, New York – December 30, 1879) was an American politician from New York.
He married Eliza Ann Wainwright (1819–1891), and they had three children.
About 1844, he was Inspector of Boats on the Canals, at Whitehall. In 1849, he was employed by the Saratoga and Whitehall Railroad Company.
He was a member of the New York State Assembly (Washington Co., 2nd D.) in 1855.
He was a member of the New York State Senate (13th D.) in 1856 and 1857.
He and his wife were buried at the Boardman Cemetery in Whitehall.