FitzGerald, Maurice fitz Thomas (c.1321–1390), 4th earl of Kildare , justiciar, was the third of three sons of Thomas fitz John FitzGerald (qv), 2nd earl of Kildare, and his wife Joan (d. 1328), daughter of Richard de Burgh (qv), 3rd earl of Ulster. He succeeded to the earldom on the death of his brother Richard (July 1331). Although Richard had been granted livery and possession of his lands while still a minor, the Kildare lands in Kildare and Offaly as well as manors in Limerick were granted to John Darcy (qv), during the new earl's minority. Darcy had married the widowed countess of Kildare in July 1329 and retained possession of the Kildare lands till Maurice was granted livery of his lands (August 1342).
Kildare was one of several Irish magnates, led by Maurice fitz Thomas FitzGerald (qv), 1st earl of Desmond, who were dissatisfied with the policies of the justiciar, Ralph Ufford (qv). In October 1344 the pope gave a dispensation for the marriage of Desmond's daughter with the earl of Kildare. This marriage alliance seems to have been Desmond's idea, but Ufford reacted by arresting Kildare and charging him with treason. In addition, the liberty of Kildare was removed for alleged misdeeds. Following Ufford's death in May 1346, Kildare was released on finding sureties of good behaviour. He was summoned to England in 1346 but was unable to leave because of repeated Irish raids and the justiciar's campaign against the O'Mores of Laois. He did leave for Calais (May 1347) and joined the king in the siege of that city. Kildare's service at Calais proved his loyalty, and he was restored to royal favour as indicated by his marriage to Elisabeth, daughter of Bartholomew, Lord Burghersh, the king's chamberlain. He was knighted at Christmas 1347 and a full pardon followed for all the crimes he had been charged with (April 1348), though royal generosity did not extend to restoring the liberty of Kildare.
When Kildare returned to Ireland he quickly set about securing his lordship. In 1350 he received indentures from two Gaelic lords who swore to support him against all but the justiciar. He entered into similar agreements with John de Bermingham and petitioned for possession of Carbury during the minority of Walter de Bermingham. Kildare's location close to Dublin allowed him to play a prominent role in the Dublin administration. From 1355 to 1375 he was often appointed chief governor, usually in a caretaker capacity, and even when not chief governor he usually had a seat on the council. He served as justiciar or deputy justiciar in August 1355, January–October 1356, September–November 1357, October 1360–September 1361, April–July 1372, and June–September 1376. In October 1379 he refused to serve as chief governor till the arrival of the deputy of the new lieutenant, citing the cost and the need to defend his own lands. Despite his regular service in office, Kildare was not always on good terms with the justiciar of the day. In June 1355 he had to be ordered to appear at Rathmore with troops to guard the marches. He was forbidden to leave Ireland in the 1350s by the Dublin government, and had to secure royal permission to do so, presumably to complain about the administration of the day. Sometime before June 1364 he was part of a delegation sent by the commons to the king to express concerns over the growing dissension between the Anglo-Irish and the English of the Dublin government. Clearly, Kildare took a more pragmatic approach to Anglo–Gaelic relations than did the lieutenant, Lionel of Clarence (qv), whose attitudes were put into law in the statute of Kilkenny (1366). In 1387 he was appointed to arbitrate in disputes between the earls of Ormond and Desmond. Kildare died in August 1390, leaving his earldom to his eldest son, Gerald FitzGerald (qv), and was buried in Christ Church, Dublin.