Butler, Piers (d. 1597), Butler rebel, was the eldest son of Sir Edmund Butler (qv) (d. 1601) of Cloghgrennan, Co. Carlow, and Eleanor Eustace, daughter of Rowland, Lord Baltinglass. He resided at his castle in Newstone. In spite of his father's removal from the succession to the earldom of Ormond following his rebellion in 1569, Piers remained loyal to the crown during the second Desmond rebellion (1579–83), it being reported in 1581 that he had killed a number of rebels. During the 1580s he was active in expanding the Butler lordship at the expense of the O'Byrnes of Wicklow at the behest of his uncle Thomas Butler (qv), 10th earl of Ormond. However, in August 1586, Fiach McHugh O'Byrne (qv) struck back, ambushing Piers and his younger brother James in the Wicklow mountains, injuring both siblings. In December 1587 the government imprisoned Piers in Dublin for a time, perhaps on account of his feud with the O'Byrnes.
The unexpected death of Ormond's only legitimate child in 1590 left Piers next in line for the earldom, but his father's attainder in blood disqualified him from succeeding. Piers became increasingly discontented with Ormond's failure to remedy this. He had grounds for complaint, as subsequent events demonstrated that Ormond could have used his favour with the queen to have Piers recognised as his heir. That he did not do so suggests enduring tensions between Ormond and the Cloghgrennan Butlers dating from Sir Edmund's rebellion in1569.
In 1596, despite Ormond's disapproval, Piers married Mary Butler, daughter of Edmond Butler (qv), 2nd Viscount Mountgarret. Mountgarret was known to have ambitions towards the earldom and was estranged from Ormond. More seriously, in the first half of 1596 Piers and his brother James became involved in treasonable communications with Hugh O'Neill (qv), earl of Tyrone, and his Leinster confederates Owny McRory O'More (qv), Domhnail Spanneach MacMurrough Kavanagh (qv), and Feagh McHugh O'Byrne (Piers's old enemy). The conspirators planned a rising in south Leinster in anticipation of the landing in Ireland of the ‘second Spanish Armada’ due for late October.
The Gaelic rebels distrusted their Butler co-conspirators, rightly suspecting that they would change sides if the government promised to restore them in blood. On 3 August 1596 Piers and James swore a solemn covenant with O'Byrne on Barnacashel Hill in Shillelagh. There, O'Byrne demanded an act of rebellion from the brothers as a token of good faith. A few days later James seized and hanged six members of the royal garrison at Ballinacor while Piers attacked the town of Knockloogh. On 9 September a combined force of O'Byrnes, Kavanaghs, and Cloghgrennan Butlers assaulted Ballincor, killed the garrison, and destroyed the fort. However, Piers failed to seize the initiative within the Butler lordship or even in his own bailiwick in Carlow, either through ineptitude or because of the possibility that the rebels’ plan was to occupy the government with guerrilla warfare in the wilds of Leinster until Spanish help arrived.
In any case, Ormond moved decisively to reassert his authority, capturing Cloghgrennan and Tullow castles in September before arresting Piers' and James' father Sir Edmund in October. Meanwhile Piers held aloof from further action and let it be known that his main grievance was the government's failure to restore him in blood. However, there was no going back, Ormond having resolved that his nephews would have to be killed. Then all the rebels’ hopes were dashed when reports reached Ireland in November that the Spanish fleet had been wrecked in a storm. Piers's public appeal to the Gaelic Irish on 9 November to rise up in defence of the catholic faith failed to have any impact. Neither did he attract any support in the Butler heartlands of Kilkenny and Carlow. The rebel forces dispersed in mid-November and went into hiding.
Having narrowly avoided capture on New Year’s Eve, Piers attempted that spring to travel in disguise into Ulster. He reached the Shannon in the midlands, but was caught by Ormond's men, taken to Thurles, and beheaded there shortly before 21 May 1597. He and his wife had one daughter, Ellen.