River monitors are military craft designed to patrol rivers.
Model of USS Monitor
The Civil War era river monitor Neosho
A Mobile Riverine Force monitor using napalm in the Vietnam War
The river monitor Sava (formerly Bodrog) fired the first shots of World War I. She is now a floating museum anchored along the Sava river in Belgrade, Serbia
A monitor is a relatively small warship that is neither fast nor strongly armored but carries disproportionately large guns. They were used by some navies from the 1860s, during the First World War and with limited use in the Second World War.
USS Monitor, the first monitor (1861)
HMS Marshal Ney used a surplus 15-inch gun battleship turret.
Officers of a Union monitor, probably USS Sangamon, photographed during the American Civil War
Huáscar anchored in the harbour at Talcahuano