Duncan McMartin Jr. (1776 - October 3, 1837) was an American politician from New York.
He lived in Broadalbin, then in Montgomery Co., now in Fulton County. He married Margaret (1778-1835), and they had several children.
He was a member of the New York State Assembly (Hamilton & Montgomery Co.) in 1819.
He was a member of the New York State Senate {Eastern D.) from 1820 to 1822, sitting in the 43rd, 44th and 45th New York State Legislatures.
He was again a member of the State Senate {4th D.) from 1827 to 1830, sitting in the 50th, 51st, 52nd and 53rd New York State Legislatures.
He was buried at a cemetery now located in Perth, a town formed after McMartin's death, and which includes an area formerly belonging to Broadalbin.
| New York State Senate | ||
|---|---|---|
| Preceded by Archibald McIntyre |
New York State Senate Fourth District (Class 4) 1827–1830 |
Succeeded by William I. Dodge |