Eustace, James (1530–85), of Harristown, 3rd Viscount Baltinglass , was eldest son and heir of Sir Roland Eustace, 2nd Viscount Baltinglass, and his wife Joan, daughter of James Butler, Lord Dunboyne. The family was firmly catholic and James had as his tutor a priest and relative, Norman Eustace. In 1567 James, by now married to Mary, daughter and coheiress of Sir John Travers of Monkstown, Co. Dublin, enrolled in Gray's Inn, London. It seems to have been his experience in these years that convinced him of the need for catholic laymen to become active in the cause of religion. In March 1575 he went to Rome where he came into contact with the recently defeated rebel James fitz Maurice Fitzgerald (qv) and other Irish and English émigrés who were working for the overthrow of Elizabeth and the restoration of catholicism. On his return to Ireland in 1578 he openly attended mass and was briefly imprisoned in Dublin castle and fined 100 marks by the ecclesiastical court of high commission. On the death of his father in the following year he succeeded to the viscountcy and the family estates in the south marches of the Pale.
Baltinglass was one of the lords of Ireland to whom fitz Maurice on landing in Kerry in July 1579, addressed the call for help in restoring the catholic church in Ireland that initiated some four years of struggle in Munster. Baltinglass had some correspondence with the earl of Desmond (qv) in 1580, but the revolt that he led in July of that year seems to have been entirely autonomous, stimulated by the Desmond rebellion but unconnected with it, and the official suspicion that it was a ploy to divert troops from Munster was groundless. Baltinglass’s conspiracy was confined to Leinster. His associates included the disaffected Fiach MacHugh O'Byrne (qv), whose mounting discontent had come to a head with the appointment of Sir Henry Harrington as seneschal of Wicklow, and a number of young Palesmen attracted by his declared aim of restoring the catholic religion. He may well have believed that the active dissatisfaction of the Palesmen with cess and composition would incline them to support him, but his own stance was severely religious. Displaying a papal banner, he informed the earl of Ormond (qv) that ‘a woman uncapax of all holy orders’ could not be head of the church, and that Ireland had suffered more oppression under Queen Elizabeth than ever before (PRO, SP 63/74/64).
His incongruous alliance with the O'Byrnes paid initial dividends when Fiach MacHugh defeated a government force commanded by the new lord deputy, Grey de Wilton (qv), at Glenmalure pass on August 25. But the Pale remained loyal and the rebellion quickly collapsed. The 11th earl of Kildare's (qv) characterisation of Baltinglass seems apt: ‘a simple man without wisdom, judgement or any other qualification meet to embrace such an enterprise’ (Brady, Chief governors, 205). The discovery that some Palesmen were involved in the plot, or had foreknowledge of it (notably William Nugent (qv), brother of Lord Delvin (qv)), led Grey to believe that the conspiracy was widespread and a series of arbitrary attainders and summary executions followed, including two brothers of Baltinglass, Thomas and Walter. Baltinglass's estates were confiscated and he was excluded from the general pardon offered in the early summer of 1581. Towards the end of that year he escaped to Wexford, hid for a while in the remote Mulrankin castle and took ship for Spain in November. He was favourably received by Philip II who gave him a monthly allowance of 100 ducats, but resisted his plea to provide troops and ships to invade Ireland.
Baltinglass died in Spain on 24 November 1585. Earlier in the year he and his four surviving brothers had been attainted by act of the Irish parliament. Almost all of his forfeited estates were granted to Sir Henry Harrington, who had been active in quelling the rebellion. He died without issue and was survived by his wife who married Sir Gerald Aylmer (qv), of Donadea, two years after his death.