A scout cruiser was a type of warship of the early 20th Century, which were smaller, faster, more lightly armed and armoured than protected cruiser

Protected cruiser

The protected cruiser is a type of naval cruiser of the late 19th century, so known because its armoured deck offered protection for vital machine spaces from shrapnel caused by exploding shells above...

s or light cruiser

Light cruiser

A light cruiser is a type of small- or medium-sized warship. The term is a shortening of the phrase "light armored cruiser", describing a small ship that carried armor in the same way as an armored cruiser: a protective belt and deck...

s, but larger than contemporary destroyer

Destroyer

In naval terminology, a destroyer is a fast and maneuverable yet long-endurance warship intended to escort larger vessels in a fleet, convoy or battle group and defend them against smaller, powerful, short-range attackers. Destroyers, originally called torpedo-boat destroyers in 1892, evolved from...

s. Intended for fleet scouting duties and acting as a flotilla leader

Flotilla leader

A flotilla leader was a warship suitable for commanding a flotilla of destroyers or other small warships, typically a small cruiser or a large destroyer...

, a scout cruiser was typically armed with six to ten destroyer-type guns of 3-inch (76mm) to 4.7-inch (120mm) calibre, plus two to four torpedo tubes.

The British was the first to operate scout cruisers, with the Royal Navy

Royal Navy

The Royal Navy is the naval warfare service branch of the British Armed Forces. Founded in the 16th century, it is the oldest service branch and is known as the Senior Service...

 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

World War I

World War I , which was predominantly called the World War or the Great War from its occurrence until 1939, and the First World War or World War I thereafter, was a major war centred in Europe that began on 28 July 1914 and lasted until 11 November 1918...

, 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 Italy. With no conventional protected cruisers or light cruisers acquired between 1900 and 1920, the Regia Marina

Regia Marina

The Regia Marina dates from the proclamation of the Kingdom of Italy in 1861 after Italian unification...

instead operated a number of scout cruisers (esploratori) from 1912 onwards. Ranging in size from enlarged destroyers to substantial, light cruiser-type ships, these esploratori were also given secondary capabilities as fast minelayer

Minelayer

Minelaying is the act of deploying explosive mines. Historically this has been carried out by ships, submarines and aircraft. Additionally, since World War I the term minelayer refers specifically to a naval ship used for deploying naval mines...

s. Later esploratori, such as the Leone class

Leone class destroyer

The Leone class were a group of destroyers built for the Italian Navy in the early 1920s. Five ships were planned and three completed. All three ships were based at Massawa, Eritrea during World War II and were sunk during the East African Campaign....

, carried extremely heavy armament for their size, capable of outgunning any destroyer of the early 1920s. Ironically, with the appearance of large, heavily-armed ‘super-destroyers’, by 1938 the surviving esploratori were re-rated as destroyers.

Regia Marina

Note: this list does not include ‘super-destroyers’ rated as scouts (esploratori) by Italy.

• Agordat class - protected cruisers, rated as esploratori from 1914 to 1921
• Quarto
• Nino Bixio class
• Alessandro Poerio class - included Cesare Rossarol
  Italian cruiser Cesare Rossarol
  Cesare Rossarol was a scout cruiserIt should be noted that her sister ships, Alessandro Poerio and Guglielmo Pepe, were re-rated as destroyers in 1921 due to their light displacements. built in Sestri Ponente, Genoa, in 1913 and launched by S.A.I. Gio. Ansaldo & C. in Liguria, Italy, in 1914...
  
  
• Mirabello class
  Mirabello class destroyer
  The Mirabello class were a group of 3 destroyers built for the Regia Marina during World War I.The ships were designed as scout cruisers , essentially enlarged versions of contemporary destroyers. All ships were built by Ansaldo in Genoa...
  
  
• Aquila class
  Marasti class destroyer
  The Mărăști class were a group of destroyers built in Italy for the Romanian Navy. The ships fought in both world wars but for different owners and had a complex history.-History:...
  
  
• Leone class
  Leone class destroyer
  The Leone class were a group of destroyers built for the Italian Navy in the early 1920s. Five ships were planned and three completed. All three ships were based at Massawa, Eritrea during World War II and were sunk during the East African Campaign....
  
  
• Capitani Romani class
  Capitani Romani class cruiser
  Capitani Romani was a class of light cruisers of the Italian navy. They were essentially designed to out-run and out-gun the large new French destroyers of the Fantasque and Mogador classes. Twelve hulls were ordered in late 1939, but only four were completed, just three of these before the...
  
   - sometimes considered as light cruisers or large destroyers (World War II)

Royal Navy

• Sentinel class
  Sentinel class cruiser
  The Sentinel class was a two ship class of scout cruiser serving with the Royal Navy, and consisting of the ships HMS Sentinel and HMS Skirmisher.-History:...
  
  
• Adventure class
  Adventure class cruiser
  The Adventure class was a two ship class of scout cruiser serving with the Royal Navy in World War I, and consisting of the ships HMS Adventure and HMS Attentive.-Design:...
  
  
• Forward class
  Forward class cruiser
  The Forward class was a two ship class of scout cruiser serving with the Royal Navy in World War I, and consisting of the ships HMS Forward and HMS Foresight.-Design:...
  
  
• Pathfinder class
  Pathfinder class cruiser
  The Pathfinder class was a two ship class of scout cruiser serving with the Royal Navy in World War I, and consisting of the ships HMS Pathfinder and HMS Patrol....
  
  
• Boadicea class
  Boadicea class cruiser
  The Boadicea class was a two ship class of scout cruisers of the Royal Navy, consisting of HMS Bellona and HMS Boadicea. They were the first class to be fitted with turbine machinery, propulsion which became standard for all future cruisers...
  
  
• Blonde class
  Blonde class cruiser
  The Blonde class cruisers were a two ship class of light scout cruisers of the British Royal Navy. They were developments of the earlier Boadicea class class, though were slightly bigger with ten 4 inch guns as their main armament.-History:...
  
  
• Active class
  Active class cruiser
  The Active class was a class of three scout cruisers of the Royal Navy, built prior to the First World War, and later seeing service in that conflict...
  
  

United States Navy

• Chester class
  Chester class cruiser
  The Chester class of light cruisers were the first United States Navy vessels to be designed and designated as Light Cruisers.-External links:...
  
  - later re-rated as light cruisers