The 'Action of 26 June 1941' was an engagement between light naval vessels of the USSR and Romania on the Chilia branch of the Danube river delta near Ceatalchioi (26 June 1941).

The action resulted in a Romanian victory and the withdrawal of the Soviet vessels, one of them being damaged and later captured.

On 22 June 1941, Romania joined the German-led Axis invasion of the USSR, aiming to recover the territories of Bessarabia and Northern Bukovina which the Soviets had occupied in June 1940. Lying on the northern part of the delta, the Chilia branch separates southern Bessarabia from Romania proper, so control of this waterway was a priority for both the Romanian and the Soviet navies and led to several naval engagements.

The Romanian force involved in this action consisted of two small torpedo gunboats, V-1 and V-3, of Romania’s Danube Flotilla. These were two of the eight-strong class of such boats built in the UK during 1906/07 by the Thames Iron Works to a Romanian order. As built, these 50-ton vessels were well-armed for their size: in addition to one 47-mm naval gun and one 6.5-mm (0.26-in) machine gun, each boat carried four torpedoes: two on spars in front of the vessel and two more amidships in torpedo dropping gear (carriages). The boats were also armoured, having bulletproof sides and deck, and their maximum speed was 18 kt. By 1916, however, their spar torpedoes had been removed, leaving only the two midships torpedoes in the dropping carriages.

Opposing the Romanian vessels were four Soviet armoured motor gunboats of the BKA type, the 'Project 1125' class. These armoured boats were lighter than their Romanian counterparts, having a displacement of 30 tons. However, they were more heavily armed, carrying one 76.2-mm (3-in) gun in a tank turret as well as several machine guns.

The action took place in the early hours of 26 June, near Ceatalchioi. The Romanian motor launches, which were part of the Tulcea Tactical Group, which also included the other two boats and two river monitors, were involved in a successful Romanian landing operation on 24 June, providing gunfire support for the ground troops as they occupied the Soviet observation post of Ceatalchioi. During the night of 25/26 June, three Soviet armoured motor gunboats infiltrated in Romanian waters in order to lay a mine barrage. The action began at 01.20 on 26 June, when the commander of V-3 spotted the three Soviet boats, which were advancing in a line. The Romanian commander used his boat’s 47-mm gun to engage the boat in the centre of the Soviet line, the second shell swiftly igniting a fire aboard the Soviet vessel. The other two Soviet boats, with their mines aboard, retreated without returning fire. While retreating at full speed, the two Soviet boats briefly rammed each other, but then resumed course. One of the two boats then hit a rock, causing her to surge off the water with her engines roaring. V-3 fired seven more shells at the two retreating boats, and V-1 also opened fire. The damaged Soviet boat was ultimately captured by the Romanians, and was later repaired and commissioned into the Romanian navy as V-7.