O'Shiel, Owen (Eoghan Ó Siadhail ) (1596–1650), physician, was born in Co. Westmeath, the son of James O'Shiel, of the barony of Moycashel in that county. The family had been prominent physicians in Westmeath since the sixteenth century. Nothing is known of O'Shiel's life until 1618, when he left Ireland with £32 to study medicine at the University of Douai in the Spanish Netherlands. A namesake and possibly a relative, Eugenio O'Chiely, was chief surgeon to the Irish regiment in the Spanish service in the Netherlands at the time, and may have helped him establish himself as a student. O'Shiel remained at Douai for three years, ‘and there attended physic, having there maintained himself with the money he carried over with him’ (SP 14/121/219). In 1621 he left Douai to return to Ireland, but was detained at Dover for refusing to take the oath of allegiance to James I. In an official examination at the time he ‘confesseth himself to be of the Romish religion and so hath ever been, and being now tendered and required to take the oath of allegiance to his most excellent majesty, he absolutely refuseth to take the same oath’ (SP 14/121/219). At the time he had only 30 shillings left and was poorly dressed (‘his apparel very mean’) (SP 14/121/218). According to the ‘Aphorismical discovery’, O'Shiel was eventually released and succeeded in returning to Ireland, where he became well known for curing a seriously ill lady who had been given up for dead by many other doctors.
O'Shiel had returned to the Spanish Netherlands by 1631 and was made doctor to the regiment of Shane O'Neill, the titular earl of Tyrone. He is recorded as doctor to this regiment again in 1632, and he was also paid for duties in the royal hospital at Malines, which was very busy at that time. The ‘Aphorismical discovery’ states that he worked in this hospital for twelve years. By 1638 he had become doctor to the regiment of Colonel Owen Roe O'Neill (qv), and he may have seen action with O'Neill at the siege of Arras between June and August 1640.
After the Ulster rebellion broke out in October 1641, O'Shiel decided to return to Ireland. It is likely that he made the journey in September 1642 with Colonel Thomas Preston (qv), as he was appointed ‘chief doctor of physic in the Leinster army’ when Preston was appointed confederate general for that province's army. He served with Preston until they fell out in August 1646. In a letter written to Preston, O'Shiel ordered him to ‘abstain from all sorts of wine, only vin de pays and Rhenish wine excepted’. He warned Preston that ‘no other end can be expected than to shorten your own days, where upon you will be accessory yourself’, and concluded the letter by stating that ‘if you follow the contrary this much I discharge myself of my duty towards your honour’ (SP 63/261/190). In addition to concern at Preston's drinking, the general's less than wholehearted opposition to the Ormond peace and the fiasco of the confederate assault on Dublin also led O'Shiel to leave his service.
O'Shiel left the Leinster army to join the confederate Ulster army and serve General Owen Roe O'Neill as his personal physician. O'Neill gave his doctor the castle of Woodstock, near Athy, when he gained control of that town. In 1648, when O'Shiel was absent, his wife, Catherine, defended the castle against General Preston, who summoned her four times to surrender and then threatened to have her nephew Hugh O'Shiel hanged. She still refused to yield. When General O'Neill fell ill in Derry in August 1649, O'Shiel was again absent. However, he returned to be at O'Neill's bedside in a house by Cloughoughter Castle, where O'Neill died 6 November 1649. Thereafter O'Shiel served O'Neill's son Henry and remained with the Ulster army. He was apparently killed at the battle of Scarriffhollis, near Letterkenny in Co. Donegal, on 21 June 1650. As the ‘Aphorismical discovery’ states, ‘at least no notice was of his life ever since’.
Owen O'Shiel was a famous doctor in his lifetime and was also a committed catholic. His wife, Catherine Tyrrell, a daughter of Captain Richard Tyrrell (qv), who fought in the Nine Years War, referred in 1648 to ‘all the children’ she had had with O'Shiel, although their names are not recorded.