USS Isonomia was a gunboat in the United States Navy during the American Civil War.

Originally built as a passenger steamboat intended for merchant service under the name Shamrock, the vessel was purchased at New York from Charles S. Leary on 16 July 1864.

She served off New Inlet, North Carolina, until ordered to Key West on 18 September with special instructions to cruise in the vicinity of Nassau and the Bahama Banks.

She captured the British bark George Douthwaite which attempted to slip into the Warrior River with a cargo of sugar, rum, wool, ginger, and mahogany from Jamaica.

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