- "It's my father's sword, and his father before him. The Mormonts have carried it for five centuries. It was meant for my son, Jorah. He brought dishonor to our House... but he had the grace to leave the sword before he fled from Westeros."
- ―Lord Commander Jeor Mormont
Longclaw is a Valyrian steel bastard sword that was the ancestral weapon of House Mormont for five centuries. When Lord Jeor Mormont retired from his lordship to take the black and command the Night's Watch, he passed it to his son and heir, Ser Jorah Mormont. When Jorah went into exile after trying to sell some poachers into slavery, he left the sword and Jeor's sister Maege returned it to him at the Wall.
Years later, Jeor gave Longclaw to Jon Snow as a reward for saving his life from a wight. Before giving it to Jon he had the pommel remade, replacing the bear with a direwolf, the sigil of House Stark.
Jeor gives the sword to Jon as a reward for saving his life from a wight (and also as a symbol of his growing fatherly affection for him). Before passing it on to Jon, he remarks that the name "Longclaw" is just as suitable for a wolf as a bear. Mormont has had the pommel remade, replacing the bear with a direwolf, the sigil of House Stark. He mentions that the sword previously belonged to his son, Jorah, who out of shame left Longclaw behind when he fled Westeros. Jon politely tries to refuse, but Mormont insists he keep it.
Craster briefly takes Longclaw from Jon after the latter follows him into the woods to see what the man does with his infant sons. Jon is admonished harshly by Mormont for this, who returns the sword to him and instructs him not to lose it again.
Jon later takes Longclaw with him when he takes part in the Great Ranging beyond the Wall led by Mormont. Jon is sent with a scouting party led by Qhorin Halfhand which ambushes a group of wildlings, during which Jon takes Ygritte captive. Qhorin leaves Jon to kill Ygritte with Longclaw, but Jon cannot bring himself to do that.
Ygritte later lures Jon into a trap. He is captured by a group of wildlings led by the Lord of Bones, who take Longclaw from him. Ygritte carries Longclaw as they head back to the main camp of King-Beyond-the-Wall Mance Rayder.
As they are about to reach the camp, Ygritte playfully keeps lightly whacking Jon in the head with the flat side of the sword. He eventually dodges and slips behind her, noting that she doesn't know how to wield a sword very well. Qhorin, having also been captured, stages a fight with Jon to convince the wildlings that he is betraying his vows to desert to them, so he can infiltrate Mance Rayder's camp. Qhorin steals a sword from a guard, so Ygritte tosses Longclaw back to Jon so he can defend himself. As Qhorin intended, Jon ends up killing him, impaling him on Longclaw. This marks the first time Jon has ever killed anyone. The wildlings are thus convinced that he wants to defect, and lead Jon into the camp.
Having gained Mance Rayder's trust, Jon is given back Longclaw.
Jon carries Longclaw with him as he climbs back south over the Wall. At Queenscrown, when his true allegiance to the Night's Watch is revealed, Jon fights the wildling company he is with. Jon kills Orell with Longclaw, marking the first time he kills an opponent with the blade (Qhorin's earlier death having been staged).
Jon uses Longclaw during the Battle of Castle Black, killing several wildlings with the sword. In a duel with Styr, the Thenn manages to knock Longclaw out of Jon's hands, but Jon smashes a hammer into his skull and kills Styr. After the battle, Jon intends to find Mance Rayder. Remembering that Jeor told him never to lose the sword again, Jon gives Longclaw to Sam for safekeeping.
When the White Walkers attack Hardhome, Jon is able to defeat one in a duel using Longclaw. To the surprise of both Jon and White Walker, the Valyrian steel sword does not break after coming into contact with the White Walker's ice blade. Pressing his advantage, Jon slashes the Walker with Longclaw; the creature shatters on contact, revealing that dragonglass is not the only thing that can kill a White Walker.
After discovering Jon's body in the snow, Davos has Jon's loyalist black brothers take the body to a locked room, where he leaves Longclaw nearby. When Davos and Jon's allies are about to face off against Alliser Thorne, Davos grabs Longclaw and prepares to use it against the mutineers. He is prevented from doing so by the timely arrival of wildling reinforcements. Longclaw is then used by Jon Snow to cut the rope which drops Thorne and the mutineers to their death by hanging. A day later, Dolorous Edd is seen giving the sword to Jon as he starts to pack up to leave Castle Black.
In the Battle of the Bastards, Jon makes extensive use of Longclaw, killing many foes with it in the melee. After the Bolton army is broken by the arrival of the knights of the Vale, Jon makes his way inside Winterfell. When Ramsay Bolton makes one last defiant challenge for a one on one duel while choosing a bow and arrow for his weapon, Jon is forced to drop Longclaw in order to pick up a Mormont shield from the ground and block three arrows shot by Ramsay, until he reaches and beats Ramsay bloody with his bare hands.
While leading the ranging party beyond the Wall in order to capture a wight, Jon offers to give Longclaw back to Jorah Mormont. However, Jorah refuses, stating that he lost the right to wield the sword and any claim to it when he brought shame onto his house and gives his blessing for Jon to keep it.
Later, Jon kills a White Walker with Longclaw, which allows him to discover that once a White Walker is destroyed, all the wights turned by this Walker are immediately destroyed as well. Jon continues to use Longclaw, destroying many wights during the ensuing battle against the army of the Night King. After the battle ends, Jon uses the sword to haul himself out of the water, digging the hilt into the ice covering the lake he'd fallen into.
After reuniting with Arya at the godswood of Winterfell, Jon shows her Longclaw and asks if she is jealous. Arya remarks that it is too heavy for her. During the Battle of Winterfell, Jon uses Longclaw to kill several wights, after being knocked off of Rhaegal. During the Battle of King's Landing, Jon uses Longclaw to kill several Lannister soldiers and later a Northern soldier who attempted to rape a woman. While leaving for the lands beyond the Wall, after his exile to the Night's Watch, Jon takes the sword with him.
- "The Old Gods and the New"
- "The Prince of Winterfell"
- "Valar Morghulis"
- "Valar Dohaeris"
- "Dark Wings, Dark Words"
- "The Rains of Castamere"
- "First of His Name"
- "The Watchers on the Wall"
- "High Sparrow"
- "The Red Woman"
- "Book of the Stranger"
- "Beyond the Wall"
- "The Iron Throne"