HMS Courageous was the lead ship of her class of three battlecruisers built for the Royal Navy in the First World War. Designed to support the Baltic Project championed by First Sea Lord John Fisher, the ship was very lightly armoured and armed with only a few heavy guns. Courageous was completed in late 1916 and spent the war patrolling the North Sea. She participated in the Second Battle of Heligoland Bight in November 1917 and was present when the German High Seas Fleet surrendered a year later.

The Courageous class consisted of three battlecruisers known as "large light cruisers" built for the Royal Navy during the First World War. The class was nominally designed to support the Baltic Project, a plan by Admiral of the Fleet Lord Fisher that was intended to land troops on the German Baltic Coast. Ships of this class were fast but very lightly armoured, with only a few heavy guns. They were given a shallow draught, in part to allow them to operate in the shallow waters of the Baltic but also reflecting experience gained earlier in the war. To maximize their speed, the Courageous-class battlecruisers were the first capital ships of the Royal Navy to use geared steam turbines and small-tube boilers.