'Drosselfang' was a German and Finnish naval attempt by the torpedo boats T 30 and T 31 of Korvettenkapitän Rudolf Koppenhagen’s 6^th Torpedoboots-Flottille, supported by Finnish motor torpedo boats, to intercept and prevent a Soviet amphibious landing on the islands of Koivusaari and Piisaari off Helsinki, the Finnish capital, in the Gulf of Finland (20/21 June 1944).

The operation was unsuccessful, and T 31 was lost to a torpedo from a Soviet motor torpedo boat.