A scout cruiser was a type of warship of the early 20th century, which were smaller, faster, more lightly armed and armoured than protected cruisers or light cruisers, but larger than contemporary destroyers. Intended for fleet scouting duties and acting as a flotilla leader, a scout cruiser was typically armed with six to ten destroyer-type guns of 3-inch (76 mm) to 4.7-inch (120 mm) calibre, plus two to four torpedo tubes.
The British were the first to operate scout cruisers, when the Royal Navy acquired 15 ships divided into two distinct groups - the eight vessels all ordered under the 1903 Programme, and the seven later, heavier-armed vessels ordered under the 1907–1910 Programmes. All these ships served in World War I, when the advent of better machinery and larger, faster destroyers and light cruisers had already made them obsolete.
The other major operator of scout cruisers was the Kingdom of Italy. With no conventional protected cruisers or light cruisers planned between 1900 and 1928, the Italian Royal Navy (Italian: Regia Marina) instead operated a number of scout cruisers (esploratori) from 1912 onwards. Ranging in size from enlarged destroyers to substantial, light cruiser-like ships, these esploratori were also given secondary capabilities as fast minelayers. Later esploratori, such as the Leone class, carried extremely heavy armament for their modest size, capable of outgunning any destroyer of the early 1920s. However, by 1938 the surviving esploratori were re-rated as destroyers.
Note: this list includes all vessels rated as scouts (esploratori) by Italy.