Mortimer, Roger (1287–1330), lord of Wigmore and 1st earl of March , justiciar of Ireland, was son of Edmund Mortimer (d. 1304) and his wife Margaret, daughter of Sir William Fienes, Lord Fienes. The wardship of the extensive Mortimer lands was originally granted to Piers Gaveston (qv), but Mortimer was granted livery of his lands in May 1306, although he was still under age. His Irish lands, mainly the lordship of Laois (which he inherited through his grandmother Maud de Braose), were also restored to him in December 1307, again before he reached his majority. He maintained a close connection with the Irish lordship, marrying Joan de Geneville, granddaughter and heiress of Geoffrey de Geneville (qv), lord of Trim, before October 1306, and the couple were granted possession of the lordship of Trim in December 1307. Mortimer was in Ireland in 1308 and 1309 and served the king in expeditions to Scotland, Wales, and Gascony before returning to Ireland in 1315, where he was defeated by Edward Bruce (qv) at Kells (December) and forced to retreat to Dublin. He returned to England and was appointed lieutenant of Ireland (November 1316) to replace Edmund Butler (qv), although he did not return to Ireland with his troops till April 1317. He landed at Youghal and marched towards Limerick to meet Bruce, who had already retreated northwards.
Mortimer decided not to follow, preferring to restore order and governmental control in the south of the lordship first. He summoned a parliament to meet in Dublin in May 1317, and ordered the division of the liberty of Kilkenny among the heirs of Gilbert de Clare, earl of Gloucester. In June 1317 he fought two battles against Walter de Lacy, who supported the Bruce invasion and disputed Mortimer's claim to Trim; he pursued de Lacy into Connacht and then returned to Leinster to enforce peace in the region of Dublin. In March 1318 he brokered a peace in Connacht by granting lands to Toirrdelbhach Ó Connor (qv); this pacified the province, but at the cost of largely abandoning the royal presence in Roscommon. Mortimer was summoned back to England in May, where he generally took a neutral stance in the growing Despenser–Lancaster feud. In March 1319 he was appointed justiciar of Ireland and granted custody of the castles of Roscommon, Randown, and Athlone. Returning to Ireland in June 1319, he held a parliament at Dublin around Easter 1320 which confirmed that various English statutes should be current in Ireland and issued various ordinances dealing with administration and peace-keeping. He returned to England in December 1320, when he left Thomas fitz John FitzGerald (qv), earl of Kildare, as his deputy. In England he gravitated towards the anti-Despenser camp and eventually rebelled against the king. He was sentenced to death, but this was commuted to life imprisonment in the Tower, from which he escaped (August 1324) and went into exile in France. He returned to England (September 1326) with his lover, Queen Isabella, and deposed Edward II in January 1327. He was pardoned in February 1327 and restored to his lands, and in October 1328 he was created earl of March.
Although Mortimer held no formal post in the government of Edward III, he wielded considerable authority and seems to have been responsible for the Irish policy of the new regime. It was not well received in Ireland, which forced him to rely on the earl of Kildare, the new justiciar, for support. After Kildare's death (April 1328) he developed a new approach to Ireland: he allowed the Butlers and the Geraldines of Desmond free rein in their areas of the country, and granted the earldoms of Ormond and Desmond to the heads of the families in an effort to gain their support. These grants, by an illegitimate regime, caused difficulties between Edward III and his Anglo-Irish magnates in the aftermath of Mortimer's death. Mortimer also attempted to retain the region around Dublin as his personal territory. After the death (June 1329) of John Bermingham (qv), earl of Louth, he intervened to ensure that William de Bermingham (qv) gained custody of his brother's lands. He received custody of the lands and marriage of the earl of Kildare in January 1330 and custody of the liberty of Kildare in May, regained custody of the castle of Athlone (April), and completed his jurisdictional authority with a grant of palatine authority over all of Meath, including the de Verdon lands as well as his own lordship of Trim (April), and a similar grant for Louth (June). His excessive greed caused increasing opposition to him in England, and his regime was ended by a coup d'état led by Edward III. He was impeached, attainted, and executed on 29 November 1330. His body was buried in the church of the Grey Friars, Shrewsbury.