The Zeebrugge Raid (French: Raid sur Zeebruges; 23 April 1918), was an attempt by the Royal Navy to block the Belgian port of Bruges-Zeebrugge. The British intended to sink obsolete ships in the canal entrance, to prevent German vessels from leaving port. The port was used by the Imperial German Navy as a base for U-boats and light shipping, which were a threat to Allied shipping, especially in the English Channel. Several attempts to close the Flanders ports by bombardment failed and Operation Hush, a plan to advance up the coast in 1917, proved abortive. As shipping losses to U-boats increased, finding a way to close the ports became urgent and a raid was considered.
The first attempt on Zeebrugge was made on 2 April 1918 but cancelled at the last moment, after the wind direction changed and made it impossible to lay a smoke-screen. Another attempt was made on 23 April with a concurrent attack on Ostend. Two of three blockships were scuttled in the narrowest part of the Bruges Canal and one of two submarines rammed the viaduct, which linked the shore and the mole, to isolate the German garrison. The blockships were sunk in the wrong place and after a few days, the canal was open to submarines at high tide. British casualties were 583 men and German losses were 24 men; the raid was publicised by the British around the world as a great success and many medals were awarded.