John Cotton Mather (November 30, 1813 Deposit, Delaware County, New York – August 13, 1882 Watertown, Jefferson County, New York) was an American politician. In 1853, he was the first person tried by the New York Court for the Trial of Impeachments.
He was the son of Dr. Thaddeus Mather (1778–1854) and Sarah (Parker) Mather. In 1837, he married Alva Porter.
At the New York state election, 1847, he ran for Canal Commissioner on the Democratic and Anti-Rent tickets, but was defeated. At the New York state election, 1850, he ran again, on the Democratic ticket, and was elected, remaining in office from 1851 to 1853. In July 1853, he was impeached by the New York State Assembly, but was acquitted by the Court for the Trial of Impeachments. At the New York state election, 1853, he ran for re-election on the Hard ticket, but was defeated by Whig Cornelius Gardinier.
He was a member of the New York State Senate (4th D.) in 1858 and 1859.
In 1869, he married Helen Goulding.
State Senator Francis M. Bixby (born 1828) was his nephew.