HMS Conqueror was a British Churchill-class nuclear-powered fleet submarine which served in the Royal Navy from 1971 to 1990. She was the third submarine of her class, following the earlier Churchill and Courageous, all designed to face the Soviet threat at sea. She was built by Cammell Laird at Birkenhead.

A submarine is a watercraft capable of independent operation underwater. It differs from a submersible, which has more limited underwater capability. The term is also sometimes used historically or colloquially to refer to remotely operated vehicles and robots, as well as medium-sized or smaller vessels, such as the midget submarine and the wet sub. Submarines are referred to as boats rather than ships irrespective of their size.