The Battle of the Bay of Biscay, or Operation Bernau, was a naval action that took place on 28 December 1943 during World War II as part of the Atlantic campaign. The battle took place in the Bay of Biscay between two light cruisers of the British Royal Navy, and a destroyer and a torpedo boat flotilla of the German Kriegsmarine hoping to intercept and escort a blockade runner. The battle was fought as part of the Allied Operation Stonewall, which was to intercept German blockade runners off the west coast of France. In the confused action that followed the two British cruisers HMS Enterprise and HMS Glasgow respectively sank T26, together with her sister ship T25 and the destroyer Z27.

The German torpedo boat T26 was one of fifteen Type 39 torpedo boats built for the Kriegsmarine during World War II. Completed in early 1943, the boat was transferred to France in August. T26 helped to lay a minefield in the English Channel the following month, and later escorted a blockade runner through the Bay of Biscay. She participated in the Battle of Sept-Îles in October and was sunk two months later by a British light cruiser during the Battle of the Bay of Biscay.