Clare, Richard de (d. 1318), magnate, was the son of Thomas de Clare (qv), who was a younger brother of Gilbert de Clare, earl of Gloucester and of Hertford. Thomas had in 1276 received a speculative grant of Thomond (the rump of the O'Brien kingdom, by this time roughly corresponding to what became later Co. Clare) from Edward I. Having established a caput at Bunratty, Thomas proceeded to colonise the plain of the River Fergus but had made relatively limited progress by his death in 1287. There then followed the minority of his eldest son; but Richard succeeded his brother in 1307 and, within four years, renewed his father's endeavour to take control of his lordship of Thomond. As is clear from a fourteenth-century Thomond source, Caithréim Thoirdhealbaigh, Richard followed the example of his father in exploiting conflicts between rival branches of the O'Brien ruling dynasty (notably Clann Thaidhg and Clann Bhriain Ruaidh) and in seeking to detach prominent vassal-chiefs from O'Brien control. In 1311 Richard suffered a setback when his territory was invaded by William Liath de Burgh (qv) of Connacht. That same year, however, Richard was quick to capitalise on an outbreak of intense local war which occurred when a vassal-chief, MacNamara, rebelled against O'Brien overlordship. The reigning O'Brien, Donnchad (qv) of Clann Thaidhg, defeated MacNamara but was then slain by a rival claimant to the kingship of Thomond, who belonged to Clann Bhriain Ruaidh. It may have been at this point that Richard de Clare launched the attack in which, according to Dowling's Annals, 600 of O'Brien's followers were slain (although that source is certainly incorrect in styling Richard as justiciar). Subsequently, it appears that Richard received some MacNamara dynasts as envoys from O'Brien, who, having pursued their own negotiations, reached an agreement that Richard sought to confirm in 1316 by issuing these vassal-chiefs of O'Brien with a charter to their own lands.
In the spring of 1317 Richard wavered in his support for Clann Bhriain as the leaders of that line made overtures to Edward Bruce (qv). Later that year, however, he supported an ill-fated venture in which Clann Bhriain was severely defeated at the battle of Corcumroe. The victor was Muirchertach O'Brien (qv) of Clann Thaidhg. In the aftermath of this battle, Richard de Clare launched an offensive from Bunratty, but was defeated and slain at Dysert O'Dea on 10 May 1318. Following this overthrow, Richard's followers abandoned Bunratty, burning what they could not carry away. The O'Brien rulers, as Lydon stresses, were willing to submit to the English crown but not to accept mesne lords such as Clare. Richard's young son died in 1321 and the lordship, divided among heiresses, succumbed to the Irish advance.