Richard Mor de Burgh is the eldest son of William de Burgh and his wife, who was a daughter of Domnall Mór Ua Briain, King of Thomond.

From the death of his father in 1206 to 1214, Richard had been a ward of the Crown until he received his inheritance.

He had briefly served in 1215 in the household of his uncle Hubert de Burgh, Earl of Kent.

He was in 1223 and again in 1225 appointed Seneschal of Munster and keeper of Limerick castle.

Richard in 1224 had claimed the land of Connacht, which had been granted to his father but never, in fact, ruled by him.

He asserted that the grant to Cathal Crobdearg Ua Conchobair, the native king, after his father's death, had been on condition of faithful service, and that his son Aedh mac Cathal Crobdearg Ua Conchobair, who had succeeded him that year, had forfeited it.

He had the favor of the justiciar, Hubert de Burgh, and in May 1227 had been awarded Connacht.

Having been given custody of the counties of Cork and Waterford and all the crown lands of Decies and Desmond, he had been appointed Justiciar of Ireland from 1228 to 1232.

De Burgh followed an unsuccessful week-long siege in 1230 with the capture in 1232 of Dún Bhun na Gaillimhe (present Galway).

When in 1232 Hubert de Burgh falls from grace, Richard is able to distance himself and avoid being campaigned against by the King.