USS Whistler (SP-784) was a United States Navy patrol vessel in commission from 1917 to 1919.
Whistler was built as a private motorboat of the same name by J. E. Graves at Marblehead, Massachusetts, in 1917.
On 17 May 1917, the U.S. Navy acquired her from her owner, Lawrence F. Percival of Boston, Massachusetts, for use as a section patrol boat during World War I.
Assigned to the Boston Section of the 1st Naval District, Whistler operated from the naval district's headquarters at the Commonwealth Pier in Boston on harbor entrance patrols for the rest of World War I.
Whistler was decommissioned on 19 May 1919 and stricken from the Navy List the same day.