USS Underwriter was a 341-ton sidewheel steamer that was purchased for military use by the Union Navy during the American Civil War.

Underwriter was outfitted as a gunboat, whose primary task was to prevent ships from penetrating the Union blockade of Southern ports.

[2] Underwriter was powered by a single-cylinder steam engine of unknown type, with bore of 48 inches (120 cm) and stroke of 9 feet (2.7 m).

[4] Underwriter assisted in the capture of New Bern, North Carolina, on 13–14 March 1862, knocking out a Confederate battery along the Neuse River during the attack.

She remained in the Neuse River off New Bern performing various reconnaissance and dispatch assignments—occasionally moving to different points in the North Carolina sounds.

On 4 January 1863, she sailed up the Chowan River 15 miles beyond Winfield, North Carolina, and destroyed Confederate supplies.

They caught Underwriter crew by surprise and took her in hand-to-hand combat, killing Acting Master Jacob Westervelt and capturing most of the vessel's complement.