Gunboat, a small, lightly armed warship. Gunboats patrol rivers, harbors, and coastlines, where larger vessels cannot maneuver. The U.S. Navy first used gunboats in the Barbary Wars (1801–05). Ironclad gunboats fought on the Mississippi River in the Civil War. Japanese airplanes sank the United States gunboat Panay on the Yangtze River in China, December 12, 1937, almost provoking a war.

The last vessel specifically designed as a gunboat for the U.S. Navy was built in 1937. Navy gunboats have since been replaced by patrol boats and similar craft. U.S. Coast Guard gunboats are called cutters.