The 'Action of 9 July 1941' was a naval engagement between warships of the Soviet and Romanian navies off the Romanian port of Mangalia (9 July 1941).

When the Axis powers launched their 'Barbarossa' invasion of the USSR on 22 June 1941, Romania joined the invasion with the aims of recovering the provinces of Bessarabia and Northern Bukovina, which the USSR had seized during the previous year. On 26 June, Soviet vessels of Black Sea Fleet unsuccessfully attacked the Romanian port of Constanța, resulting in the loss of the destroyer leader Moskva to Romanian mines. This loss led Vitse Admiral Filipp S. Oktyabrsky to be much more cautious in the use of his fleet’s surface warships.

On 9 July 1941, one week after Romania launched 'München', with German support, to retake its lost territories, the Romanian navy’s 250-ton class torpedo boat Năluca, under the command of Căpitan de marinâ Horia Popovici, and the motor torpedo boats Viscolul and Vijelia were informed by the Romanian gunboat Stihi that the periscope of a Soviet submarine had been sighted off Mangalia. Năluca was the first to arrive on the scene and subsequently spotted and engaged the Soviet 'Shchuka' class submarine Shch-206 under the command of Captain S. A. Karakai. In the first part of the engagement, Năluca attacked the submarine with 20-mm cannon fire, but the latter submerged in order to escape. Soon joined by the two motor torpedo boats, the Romanian torpedo boat subsequently used depth charges, and at 14.56 the Soviet submarine was confirmed sunk by Viscolul, none of the boat’s 38-man crew surviving.

The result of this engagement secured Mangalia for the rest of World War II, no other Soviet warships being subsequently sighted near the port. It also discouraged the Soviet navy from using the medium-sized 'Shchuka' class submarines for operations near the Romanian coast, relying instead on the much smaller 'M' class submarines, as shown during the engagements of 17 December 1941 and 1 October 1942.