RFA Wave Knight is a Wave-class fast fleet tanker of the Royal Fleet Auxiliary (RFA) of the United Kingdom tasked with providing fuel, food, fresh water, ammunition and other supplies to Royal Navy vessels around the world.

The Royal Fleet Auxiliary (RFA) is a naval auxiliary fleet owned by the UK's Ministry of Defence. It is a component of His Majesty's Naval Service and provides logistical and operational support to the Royal Navy and Royal Marines. The RFA ensures the Royal Navy is supplied and supported by providing fuel and stores through replenishment at sea, transporting Royal Marines and British Army personnel, providing medical care and transporting equipment and essentials around the world. In addition the RFA acts independently providing humanitarian aid, counter piracy and counter narcotic patrols together with assisting the Royal Navy in preventing conflict and securing international trade. They are a uniformed civilian branch of the Royal Navy staffed by British merchant sailors. The RFA is one of five RN fighting arms.