John D. Long (October 27, 1838-August 28, 1915) was a U.S. political figure. He served as the governor of Massachusetts between 1880 and 1883. He later served as the Secretary of the Navy from 1897 to 1902.
Born in Buckfield, Maine, Long graduated from Harvard University in 1857 and practiced law in Maine and Massachusetts. Long then served as Speaker of the Massachusetts House of Representatives, Lieutenant Governor, Governor and Congressman from Massachusetts.
Appointed 34th Secretary of the Navy by President William McKinley 5 March 1897, Long served with vision and efficiency through the next give years, organizing the Navy for the challenges of the Spanish-American War and the expansion that followed, and laying the groundwork for the growth of the "New American Navy" fostered by his former assistant, President Theodore Roosevelt.
Long resigned in 1902, returned to Massachusetts, and died at Hingham, Massachusetts in 1915.
USS Long (DD-209) was named for him.