The Edgar class were nine first-class protected cruisers built for the Royal Navy under the Naval Defence Act of 1889.

Although the Blake-class cruisers were impressive ships and powerful, they were too large and expensive to simply repeat en masse.

The Edgar class' main armour protection was an internal protective deck, consisting of 5 in (130 mm) thick steel armour on the outboard slopes, which connected with the hull plating just below waterline level and rose up the further it extended into the ship, with 3 in (76 mm) on the flat of the deck over the magazines and machinery spaces.

Crescent and Royal Arthur were intended to operate as flagships for cruiser squadrons on foreign stations.

In order to accommodate the additional flag officers and staff in the forward part of the ship, they had a forecastle one deck higher than their other sisters'.