Tomás Óg na Fésóige Mág Samhradháin, the Third, (anglicised Thomas McGovern, Junior 'of the beard') was chief of the Irish McGovern Clan and Baron or Lord of Tullyhaw barony, County Cavan, Ireland, from 1408 until his death in 1458.
The Annals of Loch Cé for 1428 state- Aedh Og Mag Uidhir was slain by the sons of Donnchadh Ballach Magamhrain.
In 1431 there was trouble with the Maguire clan when the son of Tomás, Brian Cáech, was killed and Ballymagauran was burned.
Maguire, i.e. Thomas, proceeded with a great host into Teallach Eachdhach, to take vengeance on the inhabitants for the death of his kinsman.
The Annals of the Four Masters for 1439 state- More, daughter of Hugh Magauran, and wife of Brian Mac Manus, died.
The Annals of Ulster for 1439 state- Mor, daughter or Aedh Mag Samradhain, namely, wife of Mac Briain Mic Maghnusa, died on the 4th of the Nones 2 February.
The Annals of the Four Masters for 1445 state- Donough Ballagh Magauran, heir to the chieftainship of Teallach-Eachdhach Tullyhaw, died.
The Annals of Ulster for 1445 state- Donchadh Mag Samradhain the Freckled died this year: namely, one who was to be chief of Tellach Eathach.
In 1455 another conflict with the Maguires erupted, Maol Sheachlainn Dubh the son of Tomás was killed and Ballymagauran was burned again.
The Annals of the Four Masters for 1455 state- A war broke out between Philip, the son of Thomas Maguire, heir to the lordship of Fermanagh, and Magauran.
Philip pitched his camp at Beann-Eachlabhra; and Brian and Tuathal, Philip's sons, went forth with twelve horsemen and thirty-seven infantry, burned Magauran's town, and the greater part of his territory, and killed Melaghlin Duv Magauran and a great number of his people; after which he returned home triumphantly.
His next consort seems to have been the daughter of Corman Mac Tadhg who bore a son Maol Sheachlainn Dubh (d. 1455).
Her sons were Feidhlimidh Mág Samhradháin, the First a later chief of the clan who died in 1495, Tomás Óg and Brian.