Isaac Phelps, Jr. (April 4, 1783—June 1, 1861) was an American politician and judge from Erie County, New York.
He was elected to the 41st New York State Legislature, serving from July 1, 1817, to June 30, 1818, alongside Robert Fleming and representing Niagara, Cattaraugus, and Chautauqua Counties.
Phelps was appointed Judge of the Common Pleas of Erie County, New York in 1820.
David Eason was originally declared the winner and served part of the term, but Phelps contested the election.
It was ruled that Phelps was the winner of the election, and was seated on January 5, 1822, and served the remainder of the term, which ended on December 31, 1822.