John M. Clancy (May 7, 1837 - July 25, 1903) was a United States Representative from New York. Born in County Laois, Ireland, he immigrated with his parents to the United States and settled in New York City. He attended the public schools of Brooklyn, engaged in the real-estate business, served as an alderman of the city of Brooklyn from 1868 to 1875, and was a member of the New York State Assembly from 1878 to 1881.
Clancy was elected as a Democrat to the Fifty-first, Fifty-second, and Fifty-third Congresses (March 4, 1889-March 3, 1895); he was not a candidate for renomination in 1894 and resumed the real-estate business in New York City. He was an unsuccessful candidate for election in 1896 to the Fifty-fifth Congress and died in Butte, Montana while returning from a visit to Yellowstone Park. Interment was in Holy Cross Cemetery, Brooklyn.