'Sacco' was a German naval operation to escort the 6,951-ton blockade runner Osorno outbound to Japan from Bordeaux on the west coast of German-occupied France across the Bay of Biscay into the Atlantic, and on the return leg provide the 'Arno' escort for the inbound blockade runner Pietro Orseolo making for Bordeaux (23 March/2 April 1943).

The German escort was provided by the fleet destroyers Z 23, Z 24, Z 32 and Z 37 of Kapitän Hans Otto Erdmenger’s 8^th Zerstörer-Flottille.