Dudley Fairley Phelps (1845 in Haverhill, Essex County, Massachusetts – December 30, 1880 in New York City) was an American lawyer and politician from New York.
Phelps was the only child of the Rev. Dudley Phelps (1797–1849), a Congregational clergyman, and Ann (Kinsman) Phelps (1808–1834). He attended Andover Theologigal Seminary, and graduated from Yale College in 1853. Then he studied law in Hillsborough County, New Hampshire and Westchester County, New York, and was admitted to the bar in 1855 in Poughkeepsie, New York. In 1856, he removed to New York City and practiced law there in partnership with his Yale classmate Sherman W. Knevals (1832–1908).
From 1866 to 1870, Phelps was an Assistant United States Attorney for the Southern District of New York. In 1869, he was sent to North Carolina to take charge of the proceedings against the officers of the USS Hornet, charged with a violation of the Neutrality laws.
In 1872, he formed a new law firm "Arthur, Phelps, Knevals & Ransom" with Chester A. Arthur, his old partner Knevals, and Rastus S. Ransom (1839–1914, Surrogate of New York 1887-93).
In November 1872, Phelps was elected on the Republican ticket New York County District Attorney, and remained in office until his death, being re-elected in 1875 and 1878.