The Siege of Great Wyk was a battle of the Greyjoy Rebellion. Following the destruction of the Iron Fleet at the Battle of Fair Isle, Stannis Baratheon led the royal fleet in a counterattack and subdued Great Wyk, the largest of the Iron Islands, while Old Wyk fell to Ser Barristan Selmy. These two victories paved the way for the subsequent Siege of Pyke, which spelled the end of the ironborn rebellion.
In the books
In the A Song of Ice and Fire novels, Stannis Baratheon led an assault on Great Wyk during the Greyjoy Rebellion.