Plunket, Thomas (d. 1519), chief justice of the common bench, was son of Robert Plunket, chief justice of the king's bench (d. 1447); nothing is known of his mother. He was appointed chief baron of the Irish exchequer in 1480 and promoted to the office of chief justice of the common bench two years later. Plunket was a client of Gerald FitzGerald (qv), 8th earl of Kildare, and followed his lead in the early crises of the reign of Henry VII. He supported Lambert Simnel (qv), who landed in Ireland in 1487 claiming to be Edward, earl of Warwick, and was defeated by Henry at the battle of Stoke on 16 June 1487. Plunket was included in the general pardon promised by Henry on 25 May 1488, along with his kinsmen Edward Plunket, lord of Killeen, and John Plunket, lord of Dunsany. In July his submission was accepted by Henry's commissioner, Sir Richard Edgecombe (d. 1489), on condition that he swore an oath of loyalty and allegiance to the king. His oath notwithstanding, Plunket supported a second Yorkist pretender, Perkin Warbeck (qv), who landed in Ireland in November 1491 claiming to be Richard, duke of York. For this he was removed from office and heavily fined. His loyalty to Kildare, however, stood him in good stead and he was reappointed to office in 1498 after the earl's return to favour and power. Richard Delahide (qv) was appointed to share the office with him in 1514, presumably on grounds of age. He retired in the following year and died in 1519. He married first Janet Finglas, and secondly Helen Strangwick (neither marriage can be dated), and had children.
Ball, Judges, i, 186; CPR, Hen. VIII, 1485–94; Letters and papers illustrative of the reigns of Richard III and Henry VII, ed. James Gairdner (2 vols, 1861–3); William Campbell (ed.), Materials for a history of the reign of Henry VII from original documents preserved in the Public Record Office (2 vols, 1873–7); G.E.C., Peerage, iv, 551–2; NHI, ii, 612–18; Mary-Rose Carthy, History of Killeen castle, County Meath, Ireland (1991)