William Tynbegh, or de Thinbegh (c.1370-1424) was an Irish lawyer who had a long and distinguished career as a judge, holding office as Chief Justice of all three of the courts of common law and as Lord High Treasurer of Ireland. His career is unusual in that he left the Bench to become Attorney General for Ireland, but later returned to judicial office. He was born in Ireland to a family of Welsh origin: his surname derives from the town of Tenby in Pembrokeshire. The Nicholas Tynbegh to whom the Crown directed him to convey lands in County Meath in 1414 was presumably a family member. In 1391 he received a license to study law in England. Somewhat surprisingly (since he can only have been called to the Bar a few years previously) he was appointed Lord Chief Justice of the King's Bench for Ireland as early as 1396 and Chief Baron of the Irish Exchequer in 1397. In 1400, in an act seemingly without precedent, he resigned from the Bench to become Attorney General. He is mentioned again as Chief Baron in 1405, when he apparently received a fresh patent of appointment. In 1409, and again in 1412, he received a royal commission to act as justice of the peace in Dublin and the adjoining counties. In 1409 he sat on a three-man commission to inquire into the export of foodstuffs from Ireland without royal licence; he was then acting as Deputy Lord Treasurer. In the same year he was one of five judges who heard a case of novel disseisin against the High Sheriff of Meath. He was Seneschal of County Wexford about 1413. He returned to the Court of Exchequer for a third term as Chief Baron in 1415, and was transferred to the Court of Common Pleas (Ireland) as Chief Justice in 1419. He apparently stepped down from the latter office, but was reappointed in 1424, not long before his death. A royal writ dated 1424 refers to his appointment in the previous January, and orders that he be paid his arrears of salary. In 1421 he persuaded the Crown to pardon Ralph Drake of Athboy, who had been declared an outlaw, not because of any notorious crime, but as a fairly common legal device in civil proceedings against a debtor. In the same year he sat on a commission with Reginald de Snyterby to try