USS Elk was a steamer, originally named Countess, which was acquired by the Union Navy during the American Civil War.

Countess, a side wheel steamer, was purchased by Admiral David Dixon Porter 8 December 1863.

Assigned to the West Gulf Blockading Squadron, Elk operated in the waters off New Orleans, Louisiana, and Mobile, Alabama, and in the lower Mississippi River.

She was constantly on the move and frequently traded fire with Confederate forces, exchanging shots with batteries off Dog River 11 March 1865, and shelling enemy pickets at Cedar Point, Florida, on 18 and 19 March.

When the magazine and ordnance stores in Mobile blew up 25 May 1865 setting fire to cotton and cotton presses and causing a general conflagration, men from Elk's crew went ashore to fight fires.