- "It's the greatest armada Westeros has ever seen. With the Iron Fleet, you own the seas!"
- ―Euron Greyjoy
During the Greyjoy Rebellion, the Iron Fleet led by Lord Euron Greyjoy raids Lannisport, destroying the Lannister fleet. The Iron Fleet was later defeated by the forces of Lord Stannis Baratheon at the Battle of Fair Isle. Following the Siege of Pyke, the Ironborn ruler Balon Greyjoy sues for peace and submits to King Robert Baratheon. His youngest son and heir Theon Greyjoy is sent to live as a ward of Lord Eddard Stark.
At the Kingsmoot held after the death of Balon, Yara vows to build the "mightiest fleet" to conquer the mainland. However, she is outmaneuvered by her uncle Euron, who advocates forging an alliance with Daenerys Targaryen in order to gain access to her dragons. While Euron is being baptized by Aeron Greyjoy, Yara, Theon, and their supporters flee on the best ships in the Iron Fleet. In response, Euron orders his supporters to build another fleet and to kill his niece and nephew.
Yara and Theon's Iron Fleet sails to Essos with the intention of beating Euron to Dany, who lives in Meereen in Slaver's Bay. On the way, they stop for rest and relaxation at the Free City of Volantis. At Meereen, Yara and Theon forge an alliance with Daenerys and her advisor Tyrion Lannister. In return for recognizing the independence of the Iron Islands and helping them to overthrow Euron, Yara agrees to ferry Dany's army to Westeros and to cease raiding the mainland. Later, the Iron Fleet is seen sailing as part of a combined Targaryen armada to invade Westeros.
After Yara and Theon abscond with their best ships, Euron considers his remaining bulk of the Iron Islands' naval forces to be the real "Iron Fleet" and refers to it as such (comparable to how both Joffrey Baratheon and Stannis Baratheon considered their own fleets to be the "Royal Fleet" when they faced each other).
After Cersei Lannister declares herself queen, Euron arrives in King's Landing to offer her a marriage-alliance and his Iron Fleet. Given that Cersei has personally alienated the North, Dorne, and the Reach with blood betrayals, Euron is the only major faction left who would be willing to ally with her - and given that Yara's faction sided with Daenerys, who has allied with Cersei's younger brother Tyrion Lannister (who killed their father), Euron claims that this makes Cersei his natural ally. Cersei remains unconvinced of his trustworthiness, given that Euron killed his own brother to seize rule of the Iron Islands. He sees her point, and departs offering that he will return with a great gift to prove his worth.
The Iron Fleet, under Euron's command and having just left King's Landing, attacks a portion of the Targaryen fleet under Yara's command as it leaves Dragonstone heading to Dorne. Euron's ships launch fireballs into Yara's, crippling the Targaryen fleet and giving naval superiority to the Iron Fleet.
The Iron Fleet returns to King's Landing where Euron parades his captives through the streets - to the amusement of the citizens. Euron delivers Ellaria and Tyene to Cersei, fulfilling his promise of a gift by handing her the people responsible for the death of her daughter Myrcella. Cersei is pleased and, in turn, promises to grant his request of marriage after the war is won. Euron then steps away from the Iron Throne towards Jaime, deliberately provoking him about the fact that Cersei is going to marry him. Euron is eventually ordered to set sail again and leads the Iron Fleet west to Casterly Rock where he attacks and destroys the remainders of Daenerys' fleet who are besieging the Rock.
When Euron and Cersei take part in the parley in King's Landing, the entire Iron Fleet docked in Blackwater Bay. After Euron witnesses a wight firsthand, he claims to be leaving in fear and taking the Iron Fleet back to the Iron Islands. However, Euron secretly takes the Iron Fleet to Essos under Cersei's orders, with the intent of transporting the Golden Company to Westeros to fight for Cersei.
In the books
In the A Song of Ice and Fire novels, the Iron Fleet is the elite naval force of the ironborn. It consists of around a hundred warships dipping 100 oars or more. It is one of the three most powerful fleets of Westeros, along with the royal fleet of the crownlands and the Redwyne fleet of the Arbor.
In contrast to the show, the Iron Fleet is not the entirety or the majority of the ironborn naval forces, which according to a semi-canon source, consist of about 500 longships. However, most of these ships only dip 20 oars and are meant for coastal raiding, not pitched naval battles and ship-to-ship engagements. The Iron Fleet is a permanent military force held to belong to the Iron Islands as a whole, not individual captains or houses.
The Iron Fleet spearheads any major military action. Its job is to destroy or pin larger enemy ships, allowing smaller longships to land on the enemy shores. The Iron Fleet was comprehensively defeated in the Battle of Fair Isle during the Greyjoy Rebellion, when the Royal Fleet under Lord Stannis Baratheon and the Redwyne fleet under Lord Paxter Redwyne trapped it in a pincer movement and destroyed it. This allowed the royalist forces to attack Pyke and end the war.
Since the end of the Greyjoy Rebellion, the Iron Fleet has been rebuilt to its former size. It is commanded by Victarion Greyjoy from his flagship, the Iron Victory.
Following Balon's death, a Kingsmoot is held and one of his younger brothers, Euron Greyjoy, is proclaimed King of the Iron Islands. Euron then embarks on a massive campaign to conquer Westeros, beginning with the Shield Islands in the Reach. While a section of the Iron Fleet under Victarion draws the Shield Islanders' fleet away from the islands, a larger Ironborn force under Euron raids and pillages the Shields.
Asha (Yara's name in the books) does not steal the Iron Fleet or any part of it. She returns to Deepwood Motte with the four ships she originally had.
After capturing Oakenshield, Euron sends the Iron fleet, under the command of Victarion, on a mission to bring him Daenerys Targaryen from Meereen. Unlike in the TV series, Euron intends to marry her, not Cersei, as his Queen.
Unlike in the show, while the Iron fleet is away, Euron does not order to build even one additional ship (let alone one thousand), because he still has hundreds of ships at his disposal - sufficiently for the next stage of his campaign against the Reach.
At the beginning of the voyage to the Slaver's Bay, the Iron fleet consists of 93 ships. Nearly half of them are lost on the way, but Victarion does not despair. The remaining fleet continues, capturing several cogs and galleys along the way. By the time the fleet reaches Meereen, it consists of 61 ships.
Ships captured by Victarion Greyjoy on the way to the Slaver's Bay:
- Noble Lady, a merchant ship
- Ghiscari Dawn, a slaver galley. Renamed "Red God's Wroth"
- Dove, a Myrish cog. Renamed "Shrike"
- A Ghis galley, renamed "Shade"
- A Ghis galley, renamed "Ghost"
- Willing Maiden, a galley from Yunkai. Renamed "Slaver's Scream"
Other ironborn ships
Other ships captained by ironborn, which are not part of the Iron fleet:
- Sea Song, captained by Lord Rodrik "the Reader" Harlaw
- Thunderer, captained by Lord Dunstan Drumm
- Nightflyer, captained by members of House Blacktyde
- Silverfin, captained by members of House Botley
- Silence, captained by Euron Greyjoy
- Black Wind, captained by Asha Greyjoy
- Great Kraken, captained by Balon Greyjoy
- Sea Bitch, captained by Theon Greyjoy