FitzGerald, Maurice fitz Gerald (1194–1257), lord of Offaly, justiciar, was son of Gerald fitz Maurice FitzGerald (qv) and his wife Eva, daughter of Robert de Bermingham. He was still a minor at the time of his father's death in 1204. Possession of his lands became a point of contention between the justiciar, Meiler fitz Henry (qv), and William Marshal (qv), earl of Pembroke and lord of Leinster (d. 1219). Custody of his lands was awarded to Marshal, but his mother's lands in Offaly remained in her possession. Maurice reached his majority in July 1215 and was granted his father's lands by November 1216, but his mother's lands remained in the possession of her third husband, Geoffrey de Marisco (qv), by customary right – a right that was upheld in court in 1226. Maurice regained these lands after the rebellion of Richard Marshal (qv), earl of Pembroke, in 1234 because de Marisco supported Marshal and forfeited his lands.
Maurice was summoned to London in October 1229 and served in the royal expedition to Poitou. He was appointed justiciar of Ireland in September 1232 to replace Richard de Burgh (qv). His period as justiciar saw the increasing sophistication of the Dublin administration as its activities and structures were brought more into line with those of England; it also saw the judicial murder of Richard Marshal. Although he himself did not commit the act, Maurice went to England in June 1234 to make peace with Gilbert Marshal (qv), earl of Pembroke, on behalf of the Anglo-Irish magnates, and again in 1240 to protest his innocence. On the latter occasion, he is said to have sworn to build a monastery for the earl's soul, and his foundation of a Franciscan friary in Sligo may be the fulfilment of that oath. His period as justiciar also saw the further expansion of the lordship, as much of Connacht was overrun by the Anglo-Irish. In 1235 he and Richard de Burgh led an army into Connacht but turned aside to punish Donnchadh Cairprech O'Brien (qv), king of Thomond, for siding with Fedlimid O'Connor (qv) (d. 1265). O'Connor was brought to peace and accepted five cantreds in Roscommon as his lordship, although he rebelled again and was temporarily deposed by Maurice before finally accepting the situation in 1237. Maurice profited personally from the conquest of Connacht as he was the major beneficiary of land grants around Sligo by Hugh de Lacy (qv), earl of Ulster. He was also deeply involved in the attempted conquest of Cenél Conaill (Donegal) and Cenél nEógain (Tyrone), as he attempted to make good a speculative grant of this region. In 1238 he joined de Lacy in a campaign to depose, temporarily as it turned out, Domnall MacLoughlin (qv), king of Cenél nEógain, in favour of Brian O'Neill (qv). Maurice was ordered to provide troops for the king's campaign in Gascony in 1243, and his eldest son, Gerald, seems to have died on this expedition. In the same year, Maurice was authorised to seize the castles of Richard de Burgh, who had also died on the Gascon expedition. In 1244 Maurice was summoned to serve the king in Wales and went with a mixed force of Anglo-Irish and Gaelic troops, led by Fedlimid O'Connor, and apparently gained the king's displeasure for his treatment of his Gaelic troops.
Maurice was replaced as justiciar by John FitzGeoffrey (qv) in November 1245. This merely freed him to pursue the conquest of western Ulster. From his base in Sligo, he campaigned regularly in Cenél Conaill and Cenél nEogáin; but despite regular victories, he could not gain a permanent foothold in the region. In 1249 he led an army into Connacht to avenge the death of Gerald de Bermingham, and joined with the justiciar to depose Fedlimid O'Connor, who however was restored a year later by Brian O'Neill. The last seven years of his life were spent attempting to gain a foothold against Brian, but when Maurice FitzGerald died in 1257 he had achieved no permanent successes. He was buried in the Franciscan friary in Youghal, which he had founded in 1253, and his lands passed to his grandson, Maurice (qv) (d. 1268).