HMS Conqueror ("Conks") was a nuclear-powered fleet submarine that served in the Royal Navy from 1971 to 1990. She was built by Cammell Laird in Birkenhead. As of 2009, she is the only nuclear-powered submarine to have engaged an enemy ship with torpedoes, sinking the cruiser ARA General Belgrano with two mark 8 torpedoes. She is one of only two submarines which have sunk a warship since World War II, the other being the Pakistani Navy's PNS Hangor.
Conqueror was the third of the class, the other two being and .
The main aim of these submarines was to face the Soviet threat at sea by attacking other ships and submarines, and spying on Soviet nuclear-armed submarine movements.
Conqueror, commanded by Commander Chris Wreford-Brown, was most famously deployed during the Falklands War, setting sail from Faslane Naval Base on the Gare Loch in Scotland on 3 April 1982, one day after the Argentine invasion. Conqueror arrived in the exclusion zone around the Falklands twenty-one days later. She was ordered to scan the area for Argentine shipping, particularly the Argentine aircraft carrier, ARA Veinticinco de Mayo (the "25th of May"). On 30 April, she spotted the Argentine light cruiser, ARA General Belgrano. Belgrano was sailing southwest of the Falklands, just outside the exclusion zone imposed by the British on all shipping and approaching the Task Force, while the ARA Veinticinco de Mayo was approaching from the north. British admiral, Rear Admiral J. F. Woodward, requested permission from the British government to sink Belgrano. After some debate he was allowed to proceed, though while this was going on the Belgrano retired from its attack position since the ARA Veinticinco de Mayo was not ready. Finally, the message to engage the Belgrano was sent from Northwood, the Royal Navy's fleet command centre in the United Kingdom to Conqueror.

The basis for this decision was that the Royal Navy feared a pincer-style attack with Belgrano attacking from the south, and the Veinticinco de Mayo from the north. Also Belgrano could have escaped from Conqueror by sailing across nearby shallow waters, and it could then have attacked the British Task Force.
The scene was now set, and on 2 May Conqueror became the first nuclear-powered submarine to fire in anger when she launched three Mark 8 torpedoes at Belgrano, two of which struck the ship and exploded. Twenty minutes later, the ship was sinking rapidly and was abandoned by the crew. Due to electrical failure the General Belgrano was unable to issue a Mayday signal, and this, combined with poor visibility, meant that the two escorting destroyers were unaware of the sinking until some hours later. A total of 323 men were killed.
Conqueror's war did not end there. The crew of the submarine had to face Argentine Air Force attempts to locate the boat in the days after the attack, which had shocked the Argentine people and ruling dictatorship. Conqueror did not fire again in anger throughout the war, but the crew did provide valuable help to the task force by using their sophisticated monitoring equipment to track Argentine aircraft departing the mainland.

After the war, Conqueror returned to Faslane, flying the Jolly Roger, a customary act of Royal Navy submarines after a "kill". When asked about the incident later, Commander Wreford-Brown responded, "The Royal Navy spent thirteen years preparing me for such an occasion. It would have been regarded as extremely dreary if I had fouled it up".
Conqueror did not take part in any other conflicts, and was decommissioned in 1990. The periscope and captain's cabin of the submarine can be viewed in the Royal Navy's museum in Gosport.