Reuben Eaton Fenton (4 July 1819–15 August 1885) was an American politician from New York. He was a Democrat from the beginning of his political career until about 1854, when he became a Republican. In 1872 he was among the Republicans opposed to President Ulysses S. Grant who joined the short-lived Liberal Republican Party.

Fenton was born in Cattaraugus County, New York and later became a resident of Jamestown in Chautauqua County, New York. Fenton was governor of New York from 1865 to 1868. He also served in the state assembly (1850), the United States Senate (1869–1875), and the United States House of Representatives (1853 to 1855 and 1857 to 1865). In 1868 he was named as a candidate to be Vice President but was eventually replaced as the Republican vice presidential candidate by Schuyler Colfax. He died in Jamestown, New York.

Fenton was one of the founders of the Republican Party and was an advocate against slavery. He was a friend of Abraham Lincoln. Fenton was known as "the soldiers' friend" for his efforts to help returning Civil War veterans. Fenton worked to remove tuition charges for public education, helped to establish six schools for training teachers, and signed the charter for Cornell University. As a first-term congressman, Fenton strongly opposed the Kansas-Nebraska Act of 1854 and unsuccessfully tried to persuade President Franklin Pierce and secretary of state William Marcy to oppose the bill. He was defeated for reelection that year. In 1878 he represented the United States at the international monetary conference in Paris, France.

His former home in Jamestown is the site of the Fenton Historical Society.