Jacob Aaron Cantor (December 6, 1854 – July 2, 1921) was an American lawyer and politician from New York who served as a United States representative from 1913 to 1915.

On September 25, 1897, he married Lydia Greenbaum, and they had three children: Margaret, Ruth and John.

He was Borough President of Manhattan from 1902 to 1903, elected on the fusion ticket headed by Seth Low for Mayor of New York City, nominated by the anti-Tammany Hall Democrats, Republicans and the Citizens Union.

Cantor was elected as a Democrat to the 63rd United States Congress to fill the vacancy caused by the resignation of Francis Burton Harrison, and served from November 4, 1913, to March 3, 1915.

He unsuccessfully contested the election of Isaac Siegel to the 64th United States Congress.