Selyse is the wife of Stannis Baratheon, the Lord of Dragonstone and claimant to the Iron Throne. She was born into House Florent of Brightwater Keep, a noble house of the Reach and bannermen of House Tyrell.
Selyse and Stannis have a single daughter, Princess Shireen Baratheon. The rest of Selyse and Stannis' offspring, Petyr, Tommard, and Edric, were all stillborn. She keeps their bodies in crystal containers filled with chemicals in her chambers.
Queen Selyse is present at the ritual burning of the statues of the Seven on the shores of Dragonstone, standing at the side of her husband and King. When Stannis pulls the flaming Lightbringer from one of the statues, she kneels alongside the rest of the worshippers of the Lord of Light. After the ceremony is over, Stannis extends his hand and Selyse rises to her feet to walk after him.
Melisandre notes that Selyse has failed to give Stannis a son, only stillborn boys, and that Selyse is sickly and often confined to her tower at Dragonstone.
Stannis later recalls to Ser Davos Seaworth how his wife nearly died during the siege of Storm's End during Robert's Rebellion before Davos was able to breach the lines and bring supplies in.
Depressed following his defeat at the Battle of the Blackwater, Stannis visits Selyse for the first time since returning from the battle. He finds her in her chamber, praying over a fire to the Lord of Light: Selyse is a fanatical believer in the religion of R'hllor, far more so than Stannis, and it was indeed Selyse who first invited Melisandre to Dragonstone. Stannis and Selyse do not have a loving relationship, but she reveres and is in awe of him as her king and the Lord's Chosen. She tells him not to despair despite his defeat, and he will be victorious, but he laments that he used to believe that once. Due to his extreme belief in duty, (unlike his hedonistic brother Robert) Stannis is badly shaken by the fact that he broke his marriage vows to Selyse, when he had sex with Melisandre to create the Shadow-assassin creature that killed Renly. He begins to confess to Selyse that he has sinned and shamed her, but she interrupts him and says Melisandre already told her everything - and that no act done in service of the Lord of Light can be a sin. Indeed, she wept for joy when Melisandre told her of this service she did for the Lord of Light with Stannis, and because the Red Priestess gave him a "son" (of sorts) which she never could. Stannis' face is filled with a mix of shock, disgust, and relief. Selyse had three sons with Stannis but they were all stillborn, and she walks over to a corner of her chamber where she keeps their tiny corpses preserved in glass jars. The deaths of her "sweet boys" and failure to produce a male heir deeply affected Selyse, and caused her to zealously embrace the foreign religion of the Lord of Light. She weeps, and laments that she has given Stannis nothing - he does not blame her, and with pity he says that's not true. Selyse understands he is referring to their daughter and only child, Princess Shireen Baratheon. She grows annoyed when she realizes he's come to see her too, and says he shouldn't waste time on such distractions, but insists that she is his daughter, and she relents because it is not her place to question her king.
On the beach of Dragonstone, Melisandre presides over a public burning, setting three people chained to stakes ablaze as an offering to the Lord of Light. One of the condemned is Queen Selyse Baratheon's own brother, condemned for his lack of faith in the Lord's power. Melisandre is surprisingly silent throughout the proceedings; it is Selyse who takes the greatest pleasure in the ritual. Afterwards, Stannis and Selyse eat dinner, with Melisandre as a guest at their table. The royal couple argue over their daughter, Princess Shireen Baratheon; Selyse believes the girl's disfigurement is a punishment from the Lord of Light, but Stannis angrily forbids his wife from trying to physically chastise their daughter for her perceived faults. Selyse switches tactics and suggests that Melisandre speak to Shireen.
Queen Selyse speaks to Melisandre, who is enjoying a bath. She quips that the Lord of Light told her to enjoy it as it was the last time she would have a good bath, but the joke goes over Selyse's head. To cement Selyse's position as Melisandre's most devoted follower, the Red Priestess tells her about using potions and illusions in serving the Lord of Light and that a bit of pageantry and deception in helping converts see the truth will be forgiven later on. Selyse asks her if she used the potions when she slept with Stannis, to which she replies that she did not. Selyse then remarks on her desire to leave their daughter Shireen behind when they go to the North but Melisandre is as dismissive about Shireen's "heresy" as she always is, and assures Selyse that Shireen will be needed where they are going.
Selyse accompanies Stannis to the North in his defense of the Night's Watch against the wildlings. She is present at the Watch's funeral for their fallen brothers.
Selyse, alongside her daughter, are present when Mance Rayder is executed by Stannis Baratheon for refusing to bend the knee. She expresses joy as Melisandre speaks of the Lord of Light and when Mance begins to be consumed by the flames.
Selyse finds her daughter teaching Gilly letters so that she may learn to read. The queen disapproves of such action, telling Shireen that her father conquered Gilly's "people" and that as a wildling she is still dangerous. Shireen attempts to defend Gilly, but Selyse simply scolds her for being naive, despite all her knowledge gained from her books.
With an excruciating reluctance, Stannis offers their daughter to Melisandre to sacrifice her to R'hllor, in order for his prophecy to become true. When the ceremony begins, Selyse at first stands firm her belief that this is the right thing to do. However, as Shireen is tied to the pyre, she begins to squirm and scream, pleading to her mother and father for her life. When the flame is lit and Shireen continues her cry for help, Selyse has a drastic change of heart and begins to implore Stannis to stop the sacrifce. As her implores turn into a beg, Stannis remains unresponsive. When Stannis does not respond to her pleas, Selyse frantically runs toward the sacrificial pyre in a last, desperate attempt to stop the ceremony, but is stopped by equally distraught Baratheon soldiers. As Shireen's screams die away with her, Selyse looks up in horror at her corpse, letting out a scream, while Stannis turns away with tears welling in his eyes - a rare occurance for someone seemingly emotionless.
Faced with the enormity of what she's done, Selyse shortly thereafter hangs herself in a copse of trees near the Baratheon camp. Stannis is shaken when his scouts discover her body, and Melisandre in turn flees the scene.
The wife of Stannis Baratheon, Selyse was much more devoted than Stannis to the Lord of Light. She initially supported all of Melisandre's exhortations, including sacrificing their only child, to help Stannis win the throne. But during Shireen's burning, Selyse had a change of heart. She was found hanging from a tree the day after Shireen's death.