USS Shadow III (SP-102) was an armed motorboat that served in the United States Navy as a patrol vessel from 1917 to 1919.

Shadow III was built as a civilian motorboat in 1916 by the Purdy Boat Company, at Miami, Florida.

The U.S. Navy purchased Shadow III from Purdy on 12 June 1917 for use as a patrol boat during World War I.

Shadow III patrolled the Florida coast off Miami during World War I.

After the war, she acted as an aircraft crash boat for Naval Air Station Miami, Florida.