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.

[2] The U.S. Navy acquired her from her owner either on or before 10 May 1917[3] or on 14 May 1917[1] 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[6] and was placed in service on 10 May 1917[7] or was commissioned on 10 August 1917.

Sources differ on the timing and nature of the end of Ellen's naval service.