Olenna Tyrell was born Olenna Redwyne. She is the mother of Lord Mace Tyrell, widow of the late Lord Luthor Tyrell.
Lady Olenna Tyrell makes her appearance in the third book. She comes to King's Landing when the Lannisters and the Tyrells form an alliance. Mace Tyrell wants Margaery to marry Joffrey, but Olenna has heard stories that Joffrey is a monster. She plots with Petyr Baelish, who in a convoluted path through Ser Dontes and Sansa Stark, gets her the poison, the tears of Lys. Someone puts it in Joffrey's wine, and he dies at his wedding feast.
Lady Olenna is called the Queen of Thorns. Her husband accidentally rode his horse off a cliff while hunting, but those who know her wonder if he did it on purpose.