Jacob S. Freer (January 22, 1824 in Marbletown, Ulster County, New York – January 27, 1892) was an American physician and politician from New York.
He graduated from Geneva Medical College in 1846, and commenced the practice of medicine in Bloomingburg. Two years later he removed to Ellenville. He married Sarah J. Jackson (1828–1912), and they had several children.
He was a member of the New York State Assembly (Ulster Co., 1st D.) in 1852; and of the New York State Senate (10th D.) in 1862 and 1863.
He was buried at the Fantinekill Cemetery in Ellenville.