By the early 20th century after World War I, the direct successors to protected cruisers could be placed on a consistent scale of warship size, smaller than a battleship but larger than a . In 1922, the placed a formal limit on these cruisers, which were defined as warships of up to 10,000 tons displacement carrying guns no larger than 8 inches in calibre; heavy cruisers had 8 inch guns while those with 6-inch or 5-inch guns were light cruisers, which shaped cruiser design until the end of World War II. Some variations on the Treaty cruiser design included the German "pocket battleships" which had heavier armament at the expense of speed compared to standard heavy cruisers, and the US which was a scaled-up heavy cruiser design designated as a "cruiser-killer".
In the later 20th century, the obsolescence of the battleship left the cruiser as the largest and most powerful surface combatant after the . The role of the cruiser varied according to ship and navy, often including air defense and shore bombardment. During the Cold War, the Soviet Navy's cruisers had heavy armament designed to sink NATO carrier task forces via . The U.S. Navy built guided-missile cruisers upon destroyer-style hulls (some called "" or "" prior to the ) primarily designed to provide air defense while often adding anti-submarine capabilities, being larger and having longer-range surface-to-air missiles (SAMs) than early guided-missile destroyers tasked with the short-range air defense role. By the end of the Cold War, the line between cruisers and destroyers had blurred, with the cruiser using the hull of the destroyer but receiving the cruiser designation due to their enhanced mission and combat systems. Indeed, the newest U.S. Navy destroyers (for instance the and ) are more heavily-armed than some of the cruisers that they succeeded.
Currently only three nations operate cruisers: the , , and . ( is still in service with the Peruvian Navy, and is the last gun cruiser currently in service in any navy).
The term "cruiser" or "cruizer" was first commonly used in the 17th century to refer to an independent warship. "Cruiser" meant the purpose or mission of a ship, rather than a category of vessel. However, the term was nonetheless used to mean a smaller, faster warship suitable for such a role. In the 17th century, the was generally too large, inflexible, and expensive to be dispatched on long-range missions (for instance, to the Americas), and too strategically important to be put at risk of fouling and foundering by continual patrol duties.