The Pelorus-class cruiser was a "third-class" protected cruiser designed by Sir William White for the Royal Navy, based on the earlier Pearl-class cruisers. Eleven ships were ordered to this design in 1893 under the Spencer Programme, and were laid down 1896–1900. The first, HMS Pelorus, was commissioned in 1896.

The QF 4-inch gun Mks I, II, III were early British QF (quick-firing) naval guns originating in 1895. They all had barrels of 40 calibres length.