Battle of Fair Isle

The Battle of Fair Isle was a battle of the Greyjoy Rebellion, taking place approximately nine years before the beginning of the Game of Thrones series. After the defeat of the ironborn in the Battle of Seagard, Lord Stannis Baratheon, Master of Ships to King Robert I, smashed the Iron Fleet, paving the way for the Iron Throne to ultimately crush the rebellion.

In the books
In the A Song of Ice and Fire novels, Lords Stannis Baratheon and Paxter Redwyne are sent to deal with the Iron Fleet following the attack on Lannisport. Stannis devises a trap for Victarion Greyjoy and destroys the Iron Fleet off the coast of Fair Isle, in the Sunset Sea.