William Mason Bennett (July 11, 1869 in Nashville, Tennessee – January 16, 1930 in Manhattan, New York City) was an American lawyer and politician from New York.

He graduated from Oberlin College in 1890, and from Columbia Law School in 1893.

At the New York City mayoral election, 1917, Bennett came in fourth, behind Democrat John F. Hylan, Mitchel (who ran as an Independent) and Socialist Morris Hillquit.

In 1918 and 1920, Bennett ran in the Republican primaries for Lieutenant Governor of New York, but was defeated twice again.

On January 15, 1930, he suffered a stroke in his law office at 15 William Street, and died the next day in Broad Street Hospital in Manhattan.