Valence, Agnes de (c.1250–1309), magnate, was the daughter of William de Valence, lord of Wexford (sometimes styled earl of Pembroke), and Joan de Munchensy (granddaughter of William Marshal (qv), earl of Pembroke and lord of Leinster, d. 1219). She was also the niece of Henry III and great-niece of Edward I. Her date and place of birth are unknown, but her parents married in 1247 and her first marriage took place in 1266, which may suggest a birth date in the late 1240s or early 1250s. She was one of seven children: three sons, all of whom died without issue (John, d. 1277; William, d. 1282; and Aymer, the future earl of Pembroke, d. 1324), and four daughters (the others being Margaret, who died in childhood in 1276, Isabel, d. 1305, who married John Hastings of Abergavenny in Wales, d. 1313; and Joan, who married John Comyn of Badenoch in Scotland, d. 1306).
Agnes married three times. Her first husband was Maurice FitzGerald (qv), lord of Offaly, whom she married at Kenilworth in Warwickshire in August 1266. The marriage to the king's niece rewarded Maurice for his support of the crown in the recent civil war in England and strengthened William de Valence's position in Ireland by providing him with a powerful Irish ally. The marriage was childless and ended when Maurice was drowned in July 1268 while crossing the Irish Sea to England. Shortly afterwards she married Hugh de Balliol of Barnard Castle in Durham, elder brother of John Balliol the future king of Scots; he died in April 1271 and again the marriage was childless. She was still unmarried in December 1276 but by October 1277 she had married John d'Avesnes, lord of Beaumont, a junior member of the family of the counts of Hainault in the Low Countries. This marriage produced three children, a daughter Felicity and two sons, John and Baldwin. Agnes was widowed for the third time in 1283 and did not marry again.
Possessing a life interest in the dower lands from three marriages, Agnes was certainly a wealthy woman, although the extent of her wealth cannot be assessed accurately. It is not known what lands she held in Beaumont, but she spent long periods on the continent looking after her affairs, making three visits in the 1290s alone. From her second marriage she held extensive property in England, and she styled herself ‘lady of Balliol’. Her Irish lands were of especial importance as, under the terms of the marriage contract, Agnes retained a life interest in half her husband's lands in Limerick (the manors of Adare, Croom, Uregare, Athlacca, Castleroberts, and Grean) and the more usual one-third dower in Maurice's lands in Kildare (one third of the manors of Maynooth, Rathmore, and Geashill). Altogether she was in control of nearly half the lands of the Geraldines of Offaly.
After 1283 Agnes faced a challenge to her possessions in Limerick from Gerald fitz Maurice FitzGerald (qv), her husband's son by an earlier marriage. His claims ended with his death in 1287, but were succeeded by others, far more serious, from John fitz Thomas FitzGerald (qv), who had inherited Gerald's lands and wished to reunite all the Geraldines’ lands under his own control. On two occasions, in 1294 and in 1303, fitz Thomas used false reports of Agnes's death as the pretext to enter and occupy her lands in Limerick and Kildare. Despite continued pressure from fitz Thomas, Agnes was still legally in possession of them when she died in December 1309. John fitz Thomas now gained full control, thrusting aside other possible claimants. Agnes's nearest heir (all of her children by John d'Avesnes having predeceased her) was her brother Aymer de Valence, earl of Pembroke and lord of Wexford and of Montignac in France. Aymer succeeded to her English lands, at Dagenham in Essex (held from the abbess of Barking) and at Great Shelford in Cambridge (held from the king and the bishop of Ely), and the manor of Hertfordingbury in Hertfordshire (held from the king). All of these Agnes had acquired by purchase.
Although an absentee from Ireland for much of her career, Agnes kept in close touch with her officials there and was determined to retain her Irish lands. She was an active and sometimes unscrupulous landholder, who used legal processes and her royal connections to full advantage whenever possible. She was also a significant member, along with others, such as her father William and brother Aymer and Geoffrey de Geneville (qv), of a group of nobility who held lands in Ireland, England, and on the continent. The history of the lordship of Ireland might have taken a different course if her marriage to Maurice FitzGerald had produced a male heir.