A destroyer tender, or destroyer depot ship in British English, is an auxiliary ship designed to provide maintenance support to a flotilla of destroyers or other small warships. The use of this class has faded from its peak in the first half of the 20th century as the roles of small combatants have evolved (in conjunction with technological advances in propulsion reliability and efficiency).
As the industrial revolution progressed, steam-powered steel ships replaced sail-powered wooden ships; but naval artillery remained the preferred weapon. The first large warship to be sunk by a torpedo was the Chilean ironclad Blanco Encalada in 1891. As major naval powers realized the vulnerability of their expensive battleships to inexpensive torpedo boats, they started building defensive flotillas of torpedo boat destroyers or destroyers for short.
The earliest torpedo boat destroyers were small, to maximize maneuverability, and powered by large steam engines, to maximize speed to intercept enemy torpedo boats before they could get close to the battleships. These torpedo boat destroyers were so full of machinery, coal, quick-firing guns and ammunition that there was not enough room for living quarters for their crew. Destroyer tenders with berthing and dining accommodations for the destroyer crews joined the fleet train of colliers accompanying the battle fleet. The destroyer tenders also carried cooks, administrative and medical personnel, and senior ratings qualified to repair the destroyer machinery. Although individual destroyers were too small for these specialized personnel, the skills of those aboard the tender were available to the whole destroyer flotilla. The tender also carried a supply of spare parts for destroyer machinery.