USS Neptune was a large steamer, with powerful guns and a large crew, acquired by the United States Navy for service with the Union Navy during the American Civil War.

At the end of the American Civil War in 1865, she returned to New York City, where she was decommissioned on 31 May 1865.

Neptune was sold at auction at New York City on 12 July 1865 to John Henderson.

She operated briefly in commercial service before being stranded in fog off Long Island, New York, on 5 December 1865.

[1] This article incorporates text from the public domain Dictionary of American Naval Fighting Ships.