HMS Dart (K21) was a River-class frigate of the Royal Navy. Dart was built to the RN's specifications as a Group I River-class frigate.

The River class was a class of 151 frigates launched between 1941 and 1944 for use as anti-submarine convoy escorts and were named for rivers in the United Kingdom. The ships were designed by naval engineer William Reed, of Smith's Dock Company of South Bank-on-Tees, to have the endurance and anti-submarine capabilities of the Black Swan-class sloops, while being quick and cheap to build in civil dockyards using the machinery (e.g. reciprocating steam engines instead of turbines) and construction techniques pioneered in the building of the Flower-class corvettes. Its purpose was to improve on the convoy escort classes in service with the Royal Navy at the time, including the Flower class.

She sailed from Blyth, Northumberland in May 1943 for Tobermory, to work-up before being sent to join a group on ocean escort of convoys. After a few weeks working-up the ship and the crew, Admiral Stephenson would then personally inspect each escort and put the Captain and crew through a stiff test before releasing them for operational service. Anti-submarine exercises were conducted on 19 June.

On 25 June Dart sailed from the Firth of Clyde escorting a mixed convoy of small RN ships to the Mediterranean Station.

Once on station Cdr. Treasure Jones formed and took command of Escort Group 49 as the group's Senior Officer – Escort (SOE). It was one of seven such British naval groups which were to escort convoys through the Mediterranean from Gibraltar to Port Said and vice versa, using Gibraltar and Alexandria as its bases. The Germans had been chased out of Africa; the Allies had landed in Sicily and were fighting their way up Italy at this time. Previous to this it had been impossible to take convoys through the Mediterranean.

As described by the Captain :

This was a comparatively peaceful mission compared to the Battle of the Atlantic, which was at its height in 1943 and 1944. It was almost like running a slow train. We would pick up our eastbound convoy just west of the Straits of Gibraltar, drop some off at Gibraltar and pick some up from there. Then, on passing Oran we would drop off ships for there and others would join us. And so on, it went at Algiers and the small ports on the north coast of Algeria, where supplies were unloaded for the armies. Then Tunis, Malta, Tobruk, Alexandria and finally Port Said, followed, of course, by the same westbound.
During this time we met up with the occasional submarine; it was mostly Italian submarines that operated here and they were rather ineffectual. Our most dangerous spot was off the African coast, between Oran and Algiers. Here we were often attacked by German aircraft based in the South of France; these aircraft usually attacked with torpedoes, but they had little success and lost many aircraft. Another spot where we sometimes met a few enemy aircraft was between Malta and Tobruk, on the African coast; these aircraft came from Crete and let go a stick of bombs from a height clear of our anti-aircraft guns.

HMS Dart convoys