She is a warrior of House Tarth, vassals to House Baratheon. After winning a tournament melee, she is made a member of King Renly Baratheon's new Kingsguard, shortly before his assassination. She becomes the sworn sword of Catelyn Stark and vows to avenge Renly's death. She is charged by Catelyn Stark to return Jaime Lannister to King's Landing, in an attempt to exchange him for her two daughters she believes are held hostage there.
Brienne is the sole surviving child and heir of Lord Selwyn Tarth of Evenfall Hall, on the island of Tarth, located in the Narrow Sea off the coast of the Stormlands. She is unusually tall and muscular for a woman by Westerosi standards and developed a taste for martial activity as a child. Brienne has grown up to become skilled at arms and dreams of becoming a knight.
Brienne's mother died when she was so young that she doesn't remember her. As the sole heir of House Tarth, she posed a fairly promising marriage prospect for men from other noble Houses, but due to her physicality and personality has never seriously pursued a marriage alliance with another House.
She is also called The Maid of Tarth, or, disparagingly, Brienne the Beauty, due to her appearance.
Brienne joins the forces of King Renly Baratheon in the War of the Five Kings. She proves herself by winning a tournament amongst his men, including a victory over Renly's favorite Ser Loras Tyrell. She asks to be named to his Kingsguard as a reward. Renly grants her request despite her gender and consequent lack of knighthood. Lady Catelyn Stark arrives in the camp to negotiate an alliance between Renly and her son, King Robb Stark. Brienne takes offense when Lady Catelyn doesn't refer to Renly as "Your Grace", and later, escorts her and Renly through the camp as they talk. She tells Catelyn just to call her Brienne, as despite her birth, she doesn't consider herself a "Lady".
Lord Petyr Baelish also visits Renly's camp, as envoy from King Joffrey Baratheon. Renly tells Petyr that he does not trust him and cites Brienne as having true loyalty. This mistrust seems well founded as Petyr offers to open the gates of King’s Landing to Renly. While in camp he also proposes that Catelyn exchange Robb's captive Ser Jaime Lannister for her daughters. Brienne also guards Renly during an unsuccessful meeting with his brother King Stannis Baratheon. Stannis threatens Renly for refusing to swear fealty to him. Renly is assassinated by a Shadow while Brienne is guarding him. He is talking to Lady Catelyn, agreeing to recognize Robb Stark as King in the North, as long as Robb gives him fealty as an overlord and recognizes his claim to the Iron Throne. Brienne is arming him for his coming battle with Stannis when the flap of the tent flutters like wind has raised it, then Melisandre's Shadow-creature materializes to stab Renly in the back, running him through. Brienne is devastated at witnessing the death, but recognizes that the Shadow had the likeness of Stannis. She cries out and catches him as he falls, getting his blood all over herself. When two other members of Renly's Kingsguard who guard the tent rush in, they blame Brienne for the death and attack her. She is forced to kill Sers Robar Royce and Emmon Cuy, and Catelyn convinces her to flee the camp, as she cannot avenge Renly if she is dead herself.
Brienne swears an oath of fealty to Catelyn, becoming her sworn sword. They travel back to Robb's camp in the Westerlands. Catelyn is devastated by news that her home Winterfell has been captured by the turncloak Theon Greyjoy and her sons made his captives. Robb, still in the midst of fighting for the Riverlands, plans to send word to a vassal in the North, the bastard of one of his commanders Roose Bolton, to free them and leaves to negotiate the surrender of the Crag.
Jaime escapes captivity, killing Torrhen Karstark in the attempt. He is soon recaptured, but Torrhen's father Lord Rickard Karstark demands his head in vengeance. Brienne guards Catelyn as she convinces Rickard to await Robb's return. As the hours until daylight stretch before them, the Karstarks are getting more violent and agitated, calling for Jaime Lannister's death. As it would be death to try to defend him, Brienne tells Catelyn that at this rate Jaime will not live enough for Robb to return. Catelyn decides to free Jaime in an attempt to exchange him for her two daughters who she believes are both being held hostage in King's Landing by the Lannisters. She orders Brienne to smuggle Jaime from the camp and deliver him to King's Landing in order to secure the safety of her daughters. Brienne travels by horse until finding a rowboat to evade pursuit. She suffers the constant antagonism of her captive as he taunts her about her appearance and her likely dismal history with the opposite sex.
When they come upon a tree with the hanging corpses of three tavern girls who have been killed by Stark forces for having relations with Lannister men, Jaime confronts her with the atrocity committed by "her side". Brienne reminds him that she is sworn to Lady Catelyn, not the Starks. Despite their need to continue, Brienne determines to give the women a decent burial and is going to cut them down, when three of the Northern soldiers who killed the women return. Jaime tries to get her to remove his chains so he can defend them, Brienne ignores him. She tells the men that she is escorting a prisoner back to Riverrun for justice. Jaime improvises that he is in chains for stealing a pig. Realizing that Brienne is a woman the Stark soldiers laugh uncontrollably. Brienne suffers it in silence, and at this even Jaime seems sympathetic towards her over this rude treatment. She deflects the men's amusement by asking about the dead women, asking if they were given a quick death, and is told two of them were. When one of the men recognizes Jaime from the Battle of the Whispering Wood, Brienne must fight and kill them, impressing Ser Jaime. She then returns to the task of cutting down and burying the tavern girls.
Jaime continues to be escorted by Brienne to King's Landing. On their way there, they are spotted by a traveler. Jaime urges Brienne to kill the travel, since he believes the man recognized him and will give away their whereabouts, but she refuses.
Later, the pair have to cross a river, which means they can either attempt a dangerous fording or take the bridge, which will probably be watched. Brienne takes the safer route of the bridge, but Jaime manages to distract her long enough to take away her spare sword and cut his bonds. Brienne and Jaime enter into an extended sword fight on the bridge. Jaime, one of the most skilled swordsmen in all of Westeros, nearly overcomes Brienne several times. However, Jaime's mobility is reduced because his hands are still manacled, and he is malnourished after having spent the past full year chained up in a cell. Jaime begins to tire, and Brienne wears him down further by making simple body-blows with kicks and punches. After a protracted fight Jaime finally slumps to the ground in exhaustion, after being thrown off balance. Just then, riders from House Bolton arrive led by a man named Locke. Jaime asks if they want to negotiate, but Locke says they'll have his head if he doesn't bring the Kingslayer back to the King in the North, so there's not much Jaime can do to dissuade him from taking them prisoner.
Brienne and Jaime were taken captive by Locke and a detachment of men from House Bolton. As they ride along, the men sing a rousing chorus of The Bear and the Maiden Fair. Tied up back to back on one of the horses, Jaime warns Brienne that when they make camp for the night, they will rape her, more than once, and that his honest advice is to give no resistance, and just think of Renly. They were only sent to capture Jaime, therefore Brienne means nothing to them, so at the slightest provocation they will kill her without hesitation. Brienne says she will fight even if they kill her, and Jaime agrees that if he were a woman, he would fight to the death before being raped too.
Later that night Locke's men make camp, and do indeed drag Brienne kicking and screaming into the bushes to gang-rape her. Jaime is disgusted by this pointless brutality, so tells Locke that Brienne is actually a noblewoman and the sole heir of Lord Selwyn Tarth, who rules the "Sapphire Isle", and her father will pay them her weight in sapphires as a ransom, provided she is unharmed. Locke agrees and calls his men back before they are able to rape Brienne, and they tie her up to a tree again.
Emboldened by his success, Jaime attempts to barter for his release by reminding Locke of the wealth and power of his own father, Lord Tywin. This has an adverse effect, however, and Locke, angered by Jaime's arrogance and complacency mutilates him by cutting off his sword hand. Afterwards while around the fire, because of his lost hand, Jaime has lost the will to live and will not eat. Although Brienne taunts him that he cannot take it when life gets real, when she asks him why he helped her escape rape, he does not reply, but starts eating.
After both are delivered to Harrenhal where Jaime's infected stump is treated, Brienne and Jamie share an intimate moment at the communal bath. Jaime first mocks Brienne, saying she was unable to protect Renly. Brienne stands up defiantly and Jaime apologizes to her. He begins to confess what really happened when he killed the Mad King. Collapsing into her arms, she calls aid for the Kingslayer, at which he whimpers to himself that his name is Jaime.
Lord Bolton allows Jaime to leave for King's Landing, but decides to keep Brienne in Harrenhal for abetting treason, in spite of Jaime's protests. Soon afterwards Lord Bolton departs to attend Edmure Tully's wedding at the Twins, leaving Brienne in Locke's custody. Locke attempts to ransom Brienne to her father, who offers 300 Gold Dragons for her return. He rejects the offer as derisory, having earlier been led to believe by Jaime that Brienne's father owned all the sapphire mines in Westeros. Instead, he throws her into a gladiatorial pit with a bear, giving her only a wooden sword to defend herself. After hearing that Brienne has been left at Locke's mercy at Harrenhal, Jaime compels his escorts to return to save her. Jaime jumps into the pit, and with the help of Steelshanks who is bound by his duty to ensure Jaime arrives in King's Landing safely, the two of them manage to escape the pit. Locke is outraged, but once again Jaime insists that Brienne accompany him, adding that Lord Bolton will not be pleased if he discovers that Locke placed his own amusement over Jaime's safe return to King's Landing. Locke relents, and Brienne and Jaime depart together.
Jaime and Brienne arrive at the gates of the Red Keep. Brienne smiles at Jaime, assuring him, after a peasant calls Jaime a "country boy".
Several weeks after their return, Brienne visits Margaery Tyrell. After enduring Olenna Tyrell's melodrama regarding her appearance and her gratitude for putting Loras Tyrell in his place, Brienne and Margaery slip off to discuss Renly's assassination. Brienne explains what she saw and how the shadow had Stannis' face, and assures Margaery that she will find a way to avenge their king. Margaery reminds Brienne that Joffrey is their king now. Brienne apologizes for any offense given, but Margaery assures her that none was taken. Brienne does not seem to notice the ostentatious statue of Joffrey only a few feet away.
Later that day, Brienne meets with Jaime near the Red Keep's Godswood to discuss the Stark girls. Jaime seems to want to forget his promise to the now-deceased Catelyn Stark, on the grounds that Arya has been missing for months and Sansa is now his sister-in-law. Brienne demands that Jaime look her in the eye and say that Sansa is safe in King's Landing; Jaime is unable to do so.
Brienne is present at the wedding feast of King Joffrey and Queen Margaery. She greets the king and queen with a bow, which earns her a brash reaction from Cersei. Joffrey mistakes her for the one who assassinated Renly Baratheon, which Margaery quickly corrects. Right after, Cersei thanks her for bringing her brother back to King's Landing safely. Brienne adds that Jaime saved her on multiple occasions, which irritates Cersei. Cersei finds it interesting that Brienne served Renly, followed by Catelyn Stark, and now Jaime. Brienne states that she does not serve her brother, but Cersei wonders if Brienne is in love with him.
Following Sansa Stark's escape from King's Landing, Jaime tasks Brienne with finding her and taking her somewhere safe, far away from his sister. As parting gifts, he gives her a new suit of armor and lets her keep his Valyrian steel sword, as it was reforged from Eddard Stark's greatsword Ice, and it would be appropriate to protect Ned Stark's daughter with a sword forged from his. He also sends her Tyrion's former squire Podrick Payne to accompany Brienne on her travels. During an emotional farewell on the Kingsroad, Jaime asks her to name the sword, and after a moment's thought, she chooses to call it "Oathkeeper".
While on the road, Podrick proves to be more a hindrance to Brienne. He has problems with his horse and accidentally sets fire to a rabbit they were cooking. Brienne tries to get rid of Podrick by releasing him from the vow he swore as her squire, but to no avail. They are bound for Castle Black, where Brienne believes Sansa may have taken refuge with her half-brother, Jon Snow. Brienne questions Podrick about his duties as squire to Tyrion. He tells her his job was mostly pouring wine, alongside other menial tasks. Brienne then asks if Podrick did anything related to combat. Podrick reveals how he killed Ser Mandon Moore of the Kingsguard by shoving a spear through his head when he tried to kill Tyrion. Brienne then allows Podrick to help her remove her armor.
Later on, Brienne and Podrick stop at an inn where they are served kidney pie made by Hot Pie, who tells them at length the process in finding the right ingredients. Brienne tells him that she is in Lady Stark's and is sworn to find and protect Sansa Stark. Hot Pie backs off, declaring the Starks traitors. As Brienne and Podrick prepare to leave the inn, Podrick reminds Brienne that telling people of their quest could be dangerous, but Brienne's honesty is swiftly rewarded when Hot Pie approaches and gives them some bread baked in the shape of a wolf. He adds that while he knows nothing of Sansa, he has seen her sister Arya, who was in the company of a man who matches the description of Sandor Clegane. Podrick, having memorized the complex family trees of the Great Houses, suggests that they head to the Eyrie, home of Lysa Arryn, Arya's aunt and the Hound's last chance of a ransom.
En route Brienne and Podrick stumble upon Arya and the Hound, who have just returned from The Eyrie. Determined to honor her vow to Catelyn Stark, Brienne urges Arya to come with her and promises to take her to safety. Arya is wary and refuses, suspecting she is working for the Lannisters. The Hound sneers that there is no safety for Arya, as all her adult relatives are dead, including Lysa Arryn, and Winterfell is a ruin. Brienne and the Hound engage in a bloody fight, which she ultimately wins by pushing him down a cliff. When she returns to Podrick, however, Arya is gone.
After failing to relocate Arya, Podrick questions Brienne if they intend to journey to Castle Black to see if Sansa Stark has been taken in by her half-brother Jon Snow. Brienne dismisses the idea of the two of them continuing to travel together, as Podrick is now hundreds of miles from the dangers of King's Landing. Podrick wishes to remain with Brienne as her squire in order to locate Sansa, but she sharply reminds him that she is not a knight, nor his mother. Brienne laments that the only thing she ever wanted was to fight for a lord she believed in, but now all the good lords are dead and the rest are monsters.
While dining at an inn, Podrick identifies Sansa Stark sitting with Petyr Baelish. Although they are surrounded by guards, Brienne approaches them and reveals to Sansa that she swore an oath to her mother to keep her safe. Petyr counters by telling Sansa that Brienne, a complete stranger, swore oaths to protect both Catelyn and Renly Baratheon and failed. Sansa rejects Brienne's offer of protection while Petyr insists that Brienne stay with their group as the roads are not safe. Sensing the trap, Brienne escapes with Podrick on stolen horses and are pursued by the guards. Brienne is forced to let Sansa and Petyr escape since she was separated from Podrick during the chase. Brienne rescues him by slaying two of the pursuing guards and the duo prepare to pursue Sansa and Petyr.
Brienne and Podrick witness Petyr and Sansa approach Moat Cailin. Realizing that following them through the castle would be futile, she decides to bypass the Moat Cailin by going around. Although Podrick is worried about losing sight of them, Brienne tells him that they don't need to follow them so closely because she knows where they are going.
Making camp, Brienne learns how Podrick became Tyrion Lannister's squire. Podrick praises Brienne's martial prowess and is quite proud to be her squire, despite her behavior towards him. Brienne apologizes for her rude behavior towards Podrick and offers to teach him how to wield a sword and ride a horse properly.
Podrick then questions Brienne about her past with Renly Baratheon. She reveals that as a young girl, her father held a ball and invited dozens of young lords in order to find a good match for her. Brienne was captivated by all the attention she was getting, but her happiness turned to embarrassment when Brienne realized they were all just toying with her. Before she could run away, Renly took Brienne into his arms and told her that those "nasty little shits aren't worth crying over" and danced with her. Brienne also acknowledges that Renly was only interested in men, but it didn't stop her from loving him. She says that there is nothing more hateful than failing to protect the ones you love, and intends to avenge Renly by killing Stannis Baratheon, whom she believes played a role in Renly's murder due to Melisandre's Shadow resembling Stannis.
Brienne and Podrick finally reach Winterfell and take a room at a nearby inn in the Winter town. Podrick muses that Sansa is home now, but Brienne counters that a Winterfell full of Boltons is hardly safe at all. When a servant comes to bring food, Brienne engages him. Although reluctant to trust southerners, the man listens to Brienne when she says she is sworn to Lady Catelyn and is impressed when she says that her death does not release her from her vows. Brienne then reveals that Sansa is in Winterfell and she needs the old man to get a message to her.
Brienne and Podrick continue to wait for Sansa's signal, watching the window of the tower at every opportunity.
Still waiting Sansa's signal, Brienne is warned by Podrick of the arrival of Stannis and what is left of his army. She reluctantly abandons her mission of saving Sansa, with the candle in the tower being lit by Sansa just a few seconds after Brienne leaves. After the battle, which resulted in the complete annihilation of the remainder of Stannis' army, Brienne finds Stannis wounded in the Wolfswood. Stannis takes her for a woman fighting for the Boltons, but Brienne tells him her name and real allegiance. Stannis confesses his involvement in the assassination of his younger brother Renly, who Brienne had sworn to protect as member of his kingsguard. Brienne draws her sword and sentences Stannis to death. When asked for any last words, Stannis urges Brienne to do her duty, after which she swings her sword at him.
With Stannis dead, Brienne and Podrick continue their search for Sansa. Eventually, they manage to find Sansa and Theon Greyjoy being apprehended by a Bolton hunting party. Brienne kills most of the soldiers on horseback, then knocks one off his horse before slitting his throat. Once all the soldiers are dead, Brienne once again offers her services to Sansa, who readily agrees this time.
Later, while making camp, Brienne informs Sansa that Arya is alive, though she was unable to find her after defeating the Hound. After resting, Brienne and Podrick accompany Sansa to meet her half-brother Jon Snow at Castle Black. However, Theon decides not to travel with them and to instead return to his family in the Iron Islands.
Brienne, Podrick and Sansa arrive at Castle Black, where Sansa and Jon are reunited. Brienne notices Tormund Giantsbane gazing at her admirably. In the meantime, Brienne confronts Davos Seaworth and Melisandre, having previously met them in the Stormlands during Renly and Stannis's parley. Having overheard Davos ask Melisandre what exactly happened, Brienne openly admits that she found and killed Stannis after he admitted to murdering Renly with blood magic. Though she admits it is in the past, she claims she will never forgive Melisandre for her role in Renly's death. Brienne later shares a meal with Jon, Sansa, Podrick, Tormund and Eddison Tollett, during which Jon receives a letter from Ramsay Bolton demanding Sansa back on threat of harming him and his friends, and displays obvious anger when Ramsay mentions letting his soldiers rape Sansa one by one.
Brienne later accompanies Sansa to the ruins of Mole's Town to meet with Petyr Baelish. Though Baelish offers to help Sansa against the Boltons, Sansa accuses him of deliberately giving her to Ramsay to further his own agendas and contemplates having Brienne kill him there and then, though she lets him go after he reveals that her great-uncle, Brynden Tully, has retaken Riverrun from the Freys. At a war council, Brienne listens to Jon, Davos and Sansa's strategies for their upcoming war with Ramsay, and is visibly concerned when Sansa claims she learned of Brynden's victory via one of Ramsay's messages. Sansa tasks Brienne with locating Brynden and recruiting him to their cause, though Brienne expresses concern at leaving Sansa, trusting Jon to protect her but remaining wary of Davos and Melisandre, who helped Stannis kill Renly, and Tormund, whose admiration of her has left her uneasy. When Brienne asks Sansa why she did not trust Jon with Baelish's information, Sansa does not answer. Brienne later leaves Castle Black with the others, starting her journey to the Riverlands with Podrick.
Lord Selwyn of Tarth's daughter, Brienne is a highborn lady who trained instead to become a warrior. Despite Lady Catelyn's death, Brienne was tasked by Jaime Lannister to uphold their oath to Catelyn by finding and protecting her daughters. Although both girls initially refused her help, she followed Sansa to Winterfell and was present when Stannis Baratheon tried to take the castle. Knowing that Stannis was responsable for the death of his brother Renly, whom she served and loved, Brienne killed Stannis. Brienne fulfilled her vow to Catelyn when sansa, on the run and in need of protection, accepted Brienne's service. At sansa's behest, she traveled to the Riverlands to peersuade Brynden "The Blackfish" Tully to help the Starks retake Winterfell. She failed to convince the Blackfish to abandon Riverrun, but Jaime Lannister allowed her to escape the siege unharmed.
Brienne has spent most of her life as the object of scorn, rejection and – at best – pity. When she tried to dress and act like a proper lady, she was met with mockery and disdain for her unattractive appearance and lack of feminine social graces; when she turned to a career more suited to her talents as a warrior, she received only contempt and resentment for her gender despite her considerable skill.
Perhaps because of this background, Brienne is as awkward in personality as she is in appearance; Catelyn Stark notices that she has none of the easy confidence of some other warrior women. She yearns for respect and acceptance from others, and easily gives her love and loyalty to the few people who treat her with any degree of genuine courtesy. Renly Baratheon, Catelyn Stark and Jaime Lannister are among those who have won Brienne's friendship and service in this manner.
She can be headstrong and judgmental, but she is also honest, straightforward, loyal and determined. Although she has received extremely poor treatment from most knights, Brienne clings to a naïvely idealized concept of knighthood. Despite – or perhaps because of – the fact that she has no expectation of ever being recognized by society for her accomplishments and strength of character, she nevertheless strives to live up to the ideal of a true knight at all times.