The second USS Ellen (SP-284) was a United States Navy patrol vessel in commission from 1917 until 1918 or 1919. Sources differ on most aspects of her history and even on her physical characteristics. Ellen was built as a civilian motorboat of the same name either in 1911 at Staten Island, New York, or in 1915 at Greenport, New York on Long Island. The U.S. Navy acquired her from her owner either on or before 10 May 1917 or on 14 May 1917 for World War I service as a patrol vessel. She served in the Navy as USS Ellen (SP-284), but sources differ as to whether she served in a non-commissioned status throughout her Navy career and was placed in service on 10 May 1917 or was commissioned on 10 August 1917.