The 'Action off Ist' was a French naval engagement against German ships in Adriatic Sea, between the islands of Skarda and Molat off the island of Ist (29 February 1944).

The action was fought between two Free French light cruisers and a German naval force of two torpedo boats, two corvettes and three minesweepers, which were escorting a freighter. In this action the French sank the freighter and one of the corvettes at no cost to themselves before withdrawing.

For 1944 operations in the Adriatic Sea, the British created the 24^th Destroyer Flotilla based at Bari in south-eastern Italy. The flotilla comprised 10 ships including three Free French destroyers in the form of Le Fantasque, Le Terrible and Le Malin. Originally completed as large destroyers, these ships had been redesignated as light cruisers in September 1943 and, under the command of Capitaine de vaisseau Pierre Lancelot, were now to operate in the northern part of the Adriatic Sea while the British concentrated on the area farther to the south in the same sea. The speed of the French destroyers, being at 37 kt the fastest in the world at the time, allowed them to react swiftly both on intelligence and to strike at targets.

On 29 February the French departed Manfredonia, some 50 miles (80 km) to the north of Bari, and headed to the north up the Adriatic. At the same time a German convoy had departed Pola, on the Istrian peninsula at the head of the Adriatic. This tactical viability of this supply convoy was based on the strength of the escort, which took the form of the torpedo boats TA 36 and TA 37 (ex-Italian 'Ariete' Stella Polare and Gladio, the submarine chasers UJ 201 and UJ 205 (ex-Italian 'Gabbiano' class corvettes Egeria and Colubrina, and three small minesweepers. These ships had been allocated to escort the 6,311-ton freighter Kapitän Diederichsen (ex-Italian Sebastiano Veniero). The German escorts had been commissioned into German service only recently, and were on just their second operation.

The two forces were heading toward each other in the dark of a night with very little moonlight. At 21.35 hours Le Terrible's radar detected possible targets farther to the north and the Free French ships turned toward them. As soon as the French had determined that the ships were not Allied units, they opened fire with the 138.6-mm (5.46-in) guns of their main armament at a range of about 9,000 yards (8230 m) just to the west of Ist Island, and took the Germ ships by total surprise. Le Malin fired on the largest of the targets, which was the freighter, and soon scored a hit. The Germans attempted to lay a smoke screen, but the destroyers made good use of their speed and soon closed on the German ships through good use of their radar. Le Terrible's fire also struck the freighter, while Le Malin concentrated her fire on the closest of the escorts. At a range of 4,500 yards (4115 m), Le Terrible fired torpedoes: the first salvo missed, but one of the second salvo hit the freighter amidships and set her on fire. Burning fiercely, the ship was soon drifting helplessly.

Meanwhile, UJ 201 was struck by Le Malin's fire and, with her range now established nicely, the German corvette was hit six more times by 90-lb (40.6-kg) shells and was soon a burning wreck. Le Malin was close enough to launch a salvo of torpedoes, and the impact and detonation of just one of these 550-mm (21.7-in) weapons was sufficient to detonate the ship’s magazine, initiating a huge explosion that lit the sky. UJ 201 sank immediately with all hands. Both Le Terrible and Le Malin then took on the rest of the German escorts. TA 36 suffered near misses and was soon hit right on the extremity of her bow, which caused minor damage. TA 37 was hit in the engine room, however, burst into flames and quickly began to slow.

The French were about to finish the German ship, but on seeing low fast-moving silhouettes of what were possibly S-boote, Lancelot decided to withdraw. what the French saw was in fact the German minesweepers arriving to help recover the crew of the stricken freighter and search for survivors of UJ 201. Lancelot headed to the south and so back to port.

Kapitän Diederichsen remained afloat for a time, but an attempt to take her in tow failed and the survivors were taken off by the German escorts. The heavily damaged TA 37 was towed successfully and made it to Pola.

The French forced remained in the Adriatic Sea for about six months engaged in tasks such as the bombardment of Zante, and on 19 March sank two Siebel ferries (SF 273 and SF 274) on their way to Pylos and crippling another two. In August the French light cruisers were moved to the west and took part in the 'Dragoon' (i) Allied landings on the south coast of France.