Horatio Seymour (May 31, 1810 - February 12, 1886) was an American politician. He was the Democratic Party nominee for President of the United States in 1868. (See U.S. presidential election, 1868)

Horatio Seymour was born in Pompe Hill , Onondaga County, New York. He served as mayor of Utica, New York from 1842 to 1843. He served as Governor of New York from 1853 to 1854 and again from 1863 to 1864. As governor of New York in 1863 to 1864, he became a leading Northern opponent of President Abraham Lincoln's administration during the American Civil War. Seymour protested Lincoln's restriction of civil liberties during the Civil War, as well as the Emancipation Proclamation and the Union's military draft.