Alfred Washington Ellet was born at Penn's Manor, Pennsylvania, on 11 October 1820. A civil engineer by profession, he was a resident of Illinois when the Civil War broke out. In August 1861, Alfred Ellet was commissioned a Captain of the 50th Illinois Infantry. When his elder brother, Colonel Charles Ellet, Jr., undertook the conversion of several river steamers to rams in the spring of 1862, Alfred Ellet became Lieutenant Colonel of Charles Ellet's U.S. Ram Fleet.

Following Charles Ellet's death in June 1862, Alfred took over the unit and was appointed Brigadier General of Volunteers the following November. He commanded the Ram Fleet and its successor organization, the Mississippi Marine Brigade, during operations on the Western Rivers until 1864, when the unit was disestablished. He resigned his commission late in that year to return to civil life. Following the Civil War, Alfred Ellet was a businessman and civic leader in El Dorado, Kansas, where he died on 9 January 1895.

USS Ellet (DD-398), which was in service in 1939-46, was named in honor of Alfred W. Ellet and other members of his family.