The only daughter of Lord Mace Tyrell and his wife, Lady Alerie only daughter, she is an intelligent and shrewd young woman, very much the protégé of her cunning grandmother, Olenna Tyrell, nee Redwyne. She is also very beautiful, with softly curling brown hair, brown eyes and a slender yet shapely figure.
Margaery was first married to King Renly Baratheon, as a pledge of loyalty from the Tyrell family. When he was killed, the Tyrells allied with the Lannisters, wedding Margaery to King Joffrey Baratheon. After Joffrey was poisoned at their wedding feast, Margaery was wed yet again, this time to Joffrey's younger brother Tommen, a little boy who was then crowned king. In the months after their marriage, the Queen Regent Cersei schemed to dispose of Margaery and the Tyrells, taking advantage of Margaery's claim to still be a maid despite her marriage to Renly. This claim may or may not be true; Margaery's maidenhead was confirmed to have been ruptured by a Septa who inspected her, but as communicated to the readers by Cersei, highborn girls often have their maidenheads broken by horseback-riding.
While Tommen's queen, she did much to curry favor with the populace, visiting local markets and buying fresh fruits, breads and fish, and ordering dresses and such from many local seamstresses, and making great public shows of charity, all while travelling with a bright and colorful retinue. Margaery suggested several activities for Tommen in an effort to shape him into a successful ruler, such as riding in sight of his subjects and observing sessions of the Small Council. Cersei forbade all of Margaery's suggestions. Later, Margaery recognized the military threat created by the ironborn invasion of the Shield Islands, and was incredulous at Cersei's lack of understanding.
Cersei accused Margaery of adultery and treason, lining up an impressive, if untrue, array of conspirators and evidence; she was arrested, and imprisoned to await trial by the Faith at the Great Sept of Baelor. While in custody, she confronted Cersei, revealing that she knew that this was all the doings of her "good-mother" (mother-in-law), and that she knew Cersei wanted to remove her from a position of influence, perhaps by arranging for her death. Later, one of Cersei's key witnesses revealed her plots under torture, and Cersei soon found herself sharing Margaery's plight. Their fate is unknown.