HMS Thermopylae (P355) was a T-class

British T class submarine

The Royal Navy's T class of diesel-electric submarines was designed in the 1930s to replace the O, P and R classes. Fifty-three members of the class were built just before and during the Second World War, where they played a major role in the Royal Navy's submarine operations...

 submarine

Submarine

A submarine is a watercraft capable of independent operation below the surface of the water. It differs from a submersible, which has more limited underwater capability...

 of the United Kingdom's Royal Navy

Royal Navy

The Royal Navy is the naval warfare service branch of the British Armed Forces. Founded in the 16th century, it is the oldest service branch and is known as the Senior Service...

 laid down on 26 October 1943 at Chatham Dockyard

Chatham Dockyard

Chatham Dockyard, located on the River Medway and of which two-thirds is in Gillingham and one third in Chatham, Kent, England, came into existence at the time when, following the Reformation, relations with the Catholic countries of Europe had worsened, leading to a requirement for additional...

, and launched on 27 June 1945. So far she has been the only ship of the Royal Navy to bear the name Thermopylae, after the Battle of Thermopylae

Battle of Thermopylae

The Battle of Thermopylae was fought between an alliance of Greek city-states, led by King Leonidas of Sparta, and the Persian Empire of Xerxes I over the course of three days, during the second Persian invasion of Greece. It took place simultaneously with the naval battle at Artemisium, in August...

.

Commissioned after the end of the Second World War, she had a relatively quiet career. She immediately joined the 3rd Flotilla

Flotilla

A flotilla , or naval flotilla, is a formation of small warships that may be part of a larger fleet. A flotilla is usually composed of a homogeneous group of the same class of warship, such as frigates, destroyers, torpedo boats, submarines, gunboats, or minesweepers...

 based in the Holy Loch

Holy Loch

The Holy Loch is a sea loch in Argyll and Bute, Scotland.Robertson's Yard at Sandbank, a village on the loch, was a major wooden boat building company in the late 19th and early 20th centuries....

.

She remained in service until December 1968 when she was put on the sale list. She was broken up at Troon

Troon

Troon is a town in South Ayrshire. It is situated on the west coast of Scotland, about eight miles north of Ayr and three miles northwest of Glasgow Prestwick International Airport. Lying across the Firth of Clyde, the Isle of Arran can be seen. Troon is also a port with freight and ferry services...

during 1971.