The Fly-class river gunboats (or small China gunboats), collectively often referred to as the "Tigris gunboat flotilla", were a class of small well-armed Royal Navy vessels designed to patrol the Tigris river during the Mesopotamian Campaign during the First World War (the China name was to disguise their function).

[a] They were fitted with one triple expansion steam engine driving one propeller housed in a tunnel to facilitate a very shallow [2 ft (61 cm)] draught.

The vessels were built by Yarrow Shipbuilders at Scotstoun, Glasgow in 1915 and 1916 and shipped to Abadan in sections where they were assembled.

They served with the Royal Navy patrolling the Tigris River until being transferred to the Army during 1918.

The Ottomans captured Firefly in December 1915 after she grounded and a shell through her boiler disabled her; her crew was evacuated.