FitzGerald, Maurice fitz Maurice (d. 1286), magnate and justiciar of Ireland, was the second son of Maurice FitzGerald (qv) (d. 1257), baron of Offaly and justiciar of Ireland, and Juliana, daughter of John de Cogan. Before he died Maurice FitzGerald granted his son lands in Connacht and an interest in some of his holdings in Munster; in return fitz Maurice quitclaimed the lands and titles of Offaly and the remaining estates in Munster in favour of his nephew, Maurice FitzGerald (qv) (d. 1268), baron of Offaly. Despite this he contested the claims to his nephew's wardship by Margaret, countess of Lincoln, one of the Marshal heiresses, from whom the barony of Offaly was held. He probably came of age in November 1259, when he was made sheriff of Connacht and granted custody of the king's castle of Athlone.
In 1260 he was defeated by Conchobair O'Brien (qv) (d. 1268) in Munster and his lands in Carbury (Co. Sligo) were plundered by Domnall Óc O'Donnell (qv). The advancement of Walter de Burgh (qv), his rival in Connacht, to the vacant earldom of Ulster in 1263 was the catalyst for the outbreak of violence in 1264 between the de Burghs and the Geraldines. De Burgh could now claim complete lordship over many of fitz Maurice's holdings in north Connacht, particularly Sligo, and south-west Ulster, and probably attempted to subordinate fitz Maurice's interests to his own. There may also have been a flirtation between the Geraldines and the Montfortians in England: the Montfort party probably encouraged the emergence of a faction in Ireland at odds with de Burgh, a staunch royalist who owed his earldom to Edward's generosity. On 6 December 1264 at Castledermot, fitz Maurice and Maurice FitzGerald captured the justiciar, Richard de la Rochelle (qv), Theobald Butler (qv) (d. 1285), and others and confined them in Lea and Dunmase castles in Offaly. De Burgh retaliated by seizing fitz Maurice's castles at Ardrahan and Lough Mask and laid waste to much of his land in Connacht. The disturbance spread and the annals state baldly that ‘a great part of Ireland was ruined between them’. Geoffrey de Geneville (qv) led an expedition against the FitzGeralds and was able to bring about a settlement between the two sides on 15 April 1265 at Dublin. In May 1265 fitz Maurice was one of those summoned to the king in England to inform him of the state of Ireland; according to an English annalist, he was present in England at or shortly after the battle of Evesham in August that year. He was certainly present at the siege of Kenilworth in August 1266, when he witnessed the marriage agreement between his nephew and his bride, Agnes de Valence (qv).
Between 1269 and 1271 fitz Maurice was again active in Connacht rebuilding his castle at Sligo after raids by O'Donnell and O'Connor. He probably accompanied the justiciar, James de Audley (qv), to Thomond in 1272, and after Audley's death on 11 June that year he was nominated as justiciar by the king's Irish council, an appointment subsequently confirmed by the king and the Lord Edward's lieutenants in England, and by Edward himself when he became king. He remained in that post until mid-April 1273. The campaign he conducted in Thomond in 1273 resulted in the taking of hostages from the O'Briens and the imposition of a fine to be allowed into the king's peace. In 1276 he led a large contingent of his Connacht vassals as part of an army gathered by the justiciar, and commanded by his son-in-law, Thomas de Clare (qv), against the Irish in the Wicklow mountains. The force was heavily defeated at Glenmalure. After returning from England to give fealty for his wife's inheritance, he accompanied Clare in his attempt to impose his lordship in Thomond (1277). He travelled to England a number of times over the following years and was probably involved in expeditions to Connacht in 1281, 1282, and 1284 and to Leinster in 1283 and 1285. He died in 1286, before 10 November.
His marriage to his first wife, Matilda the daughter of Gerald de Prendergast and widow of Maurice de Rocheford, produced one daughter, Amabilia. His second marriage to Emelina, the daughter of Stephen Longespée and Emelina de Ridelisford, also produced only one daughter, Juliana, who was married to Thomas de Clare.