Gendry is an unacknowledged bastard son of King Robert Baratheon. He is a skilled blacksmith who was traveling with Yoren to the Wall to join the Night's Watch when he was taken prisoner at Harrenhal. He later escaped with Arya and Hot Pie. After meeting with the Brotherhood Without Banners, Gendry decides to stay with the outlaw group until the red priestess Melisandre arrives to bring him to Dragonstone.
Gendry is a bastard son of King Robert Baratheon, but is unacknowledged and unaware of his lineage. Gendry did not receive the bastard surname used in the Crownlands (Waters) because he was not openly acknowledged by Robert.
His mother worked in a tavern and died when he was very young. When he was old enough, an unknown lord paid his apprentice fee so he could learn to be a blacksmith. He spent his whole life in the capital city of King's Landing working as an apprentice blacksmith under his master, Tobho Mott, to forge armor and weapons for the nobility.
Investigating the death of Jon Arryn, Lord Eddard Stark learns that he was seen visiting Tobho Mott's smithy in the city shortly before his death. Eddard also inspects the smithy. Mott tells him that Jon Arryn came to ask about new armor, but he also wanted to talk to the young man, Gendry. Eddard admires a helm that Gendry has made. Mott offers to sell it to him, but Gendry insists that it is not for sale as he made it for himself. Eddard learns that Jon wanted to know about Gendry's mother and realizes that Gendry is the bastard son of King Robert Baratheon. Eddard is at a loss as to why Jon Arryn was trying to track down Robert's bastards.
After King Robert died, the secret payments to Mott stopped so he kicked Gendry out. With no other options, Gendry decides to join the Night's Watch, and is one of the latest batch of Yoren's recruits for the Wall. He meets Arya Stark (disguised as the boy "Arry") when some of the other boys harass her about her sword. When Hot Pie bumps into him, he scares the boys off saying "When I hit that steel it sings, are you gonna sing when I hit you?"
Gendry travels north on the Kingsroad with Yoren and his recruits, befriending Arya on the journey. He is targeted by the City Watch of King's Landing because of his status as a bastard of King Robert Baratheon but remains unaware of his lineage. Yoren intimidates a pair of goldcloaks who come looking for Gendry into leaving empty handed. Gendry sees through Arya's disguise and recognizes her as a girl. She confides her identity and swears him to secrecy. The goldcloaks return with Ser Amory Lorch and a force of Lannister soldiers. They kill Yoren and capture Arya and Gendry. Arya manages to convince them that Lommy Greenhands was Gendry because he was carrying the bull's head helm Gendry made.
The prisoners are taken to Harrenhal. They are brutally tortured by Ser Gregor Clegane's men while being questioned by the Tickler. Gendry is selected as his next victim but is saved when Lord Tywin Lannister arrives and asserts that the prisoners are more useful alive.
Gendry is put to work at the castle's forge. Both the Tickler and Ser Amory are killed in suspicious circumstances. The deaths prompt Tywin to launch an investigation and he ultimately blames the Brotherhood Without Banners. Tywin leaves Harrenhal to march on the Westerlands. Arya arranges for Jaqen H'ghar to help them to escape the castle.
After escaping Harrenhal with Arya and Hot Pie, they are all captured by the Brotherhood without Banners.
While they are with the Brotherhood, Gendry helps them out by fixing some armor.
Upon learning of Gendry's desire to remain with the Brotherhood, Arya is distressed, and confronts him about it, as she had intended to bring him with her back to the Starks. Gendry explains that the Brotherhood is the closest thing he's had to a family. When Arya states that she could be his family, he reminds her that she's still the daughter of a great house and he's one of the smallfolk: she wouldn't be his family, she'd be his lady.
Gendry is out and about with Arya and members of the Brotherhood when Melisandre arrives. Arya grumbles about the presence of the red priestess, asking what all the fuss is about; Gendry quips that Arya doesn't see because she's a girl. Gendry is shocked when the Brotherhood turns him over to Melisandre in exchange for two bags of gold.
As he and Melisandre quietly traverse Blackwater Bay, she finally reveals the truth of his heritage to him by pointing out the Red Keep and identifying it as his father's house. Upon arriving at Dragonstone, Melisandre puts Gendry up in a lavish chamber and seduces him. She quickly turns the tables, tying him to the bed and proceeding to leech his blood for a ritual.
Following the incident, Gendry is relegated to a cell beneath the castle. Davos Seaworth visits him and the pair discuss the hardships of growing up in Flea Bottom. Davos asks why Gendry trusted Melisandre, to which the blacksmith admits he's never been with a woman, so although the trap was quite obvious, he took a chance. Later on, Ser Davos frees Gendry and sends him back to King's Landing in a rowboat, the only way to discreetly leave Dragonstone, although Gendry admits he doesn't know how to swim and has never been in a rowboat before.
When Stannis's army becomes snowbound on the march to Winterfell, Melisandre suggests that they sacrifice more king's blood to the Lord of Light, and Stannis initially believes she is referring to Gendry before he realizes she is referring to his own daughter, Shireen Baratheon.
Robert Baratheon's bastard son, Gendry trained as a blacksmith in Kings Landing. Upon leaving the city to jin the Night's Watch, he met and befriended Ary Stark on the road north. The two separated when Melisandre brought Gendry back to Dragonstone as a sacrifice for Stannis Baratheon. He escapeddeath when Davos Seaworth set him free.