Born in 258 AC, the only son of Lord Luthor Tyrell and Olenna of House Redwyne, called the Queen of Thorns by all who feared her tongue. He came young to the seat of Highgarden when his father rode off a cliff in pursuit of a hawk, and he wed Alerie of Oldtown, eldest daughter of Lord Leyton Hightower, who bore him four children: the crippled heir Willas, Ser Garlan called the Gallant, Ser Loras the Knight of Flowers, and his only daughter Margaery. He kept the great courtesies of the Reach and rode to every tourney in cloth-of-gold, a stout, balding lord who loved the trappings of war and the praise of his bannermen, and whose every counsel his lady mother trimmed back to something nearer wisdom before it left the hall.
In Robert's Rebellion he held for the Targaryens and led the host of the Reach against Robert Baratheon at Ashford, putting the young stag to flight in the only field he ever lost. From Ashford he marched on Storm's End and sat down before its walls with all the strength of the Reach, but he would not storm the keep nor starve Lord Stannis's garrison with sufficient zeal, and so the siege dragged on near a year until word came of the Trident and Eddard Stark rode south to lift it without a blow struck. He bent the knee to Robert and was suffered to keep Highgarden, Warden of the South still, though he never sat the new king's councils as he believed his rank deserved.
When the realm shattered after King Robert's death he wed Margaery to Renly Baratheon and rode beneath the crowned stag, only to see Renly cut down at Bitterbridge by shadow and rumour both. Through Petyr Baelish's offices he came to terms with Tywin Lannister, broke camp from Bitterbridge, and brought the Tyrell host to King's Landing in time to fall upon Stannis's rear at the Blackwater, where his horse and Tywin's foot together broke the assault and saved the boy king. For his service he saw Margaery betrothed to Joffrey, and when Joffrey choked at his own wedding she was given in turn to his brother Tommen, while a fresh Tyrell host sat down before Storm's End in a slow second siege that, like the first, took the castle by patience rather than by storm. After Lord Tywin was found dead with a quarrel in his belly, Mace was at last summoned to the Hand's seat under Tommen, and he set about packing the small council with his own creatures, vain enough to believe at last that he ruled the realm and slow enough not to see who ruled him.