William Arthur Reilly (March 6, 1903 – April 3, 1969) was an American political figure from Boston who served as the city's deputy mayor and fire commissioner and was member of the school committee and finance commission.

After graduating in 1925, Reilly became manager of his father's church music publishing business.

The nine candidate field included Frederick W. Mansfield, Malcolm E. Nichols, William J. Foley, Henry Parkman Jr., and Joseph F. O'Connell.

In 1945, Tobin, now Governor of Massachusetts, nominated Reilly to be chairman of the Metropolitan District Commission.

[4] In 1950, Mayor John B. Hynes appointed Reilly to the position of traffic commissioner.