Niall Mág Samhradháin, (anglicised Niall McGovern) was chief of the McGovern Clan and Baron or Lord of Tullyhaw barony, County Cavan from 1340 until his death in 1359.
His ancestry was Niall son of Tomás Mág Samhradháin the Second (d. 1340) son of Brian ‘Breaghach’ Mág Samhradháin (d.1294) mac Donnchadh ‘Cime’ Mág Samhradháin (d.1269) mac Giolla na Naomh Mág Samhradháin (the Second) (d.1255) mac Giolla Íosa Mág Samhradháin (d.1231) mac Giolla na Naomh Mág Samhradháin, the First, (fl.1170) mac Muireadhach Mág Samhradhán (fl.1130) mac Samhradhán (fl.1100), who were all previous chiefs of the clan. His mother was Nualaidh, the daughter of the Maguire chief and Maguire's wife Éadaoin Ó’Ceallaigh. His brothers were Tighearnán, Brian (d. 1337), Aedh (d.1351), Séan, Conchobhar, Fearghal Mág Samhradháin who also became chief and died in 1393, Maghnus 'Ruadh' Mág Samhradháin who also became chief and died in 1408, Giolla na Naomh, Tadhg Buidhe (d.1367), Maghnus Buidhe (d.1357) and Matha (d.1356).
On the death of the previous chief in 1340, his father Tomás Mág Samhradháin the Second, Niall succeeded and reigned as chief until his death in 1359.