William Mostian
William Mostian (also Mostyn) was a soldier and public official in 16th‑century Ireland. He was the son of an English father and an Irish mother. In 1585, when Tyrconnell was made County Donegal, the Lord Deputy John Perrot appointed him Sheriff of the county. This move brought him into conflict with Sir Hugh O'Donnell, the lord of Tyrconnell. O'Donnell, though allied with the Crown, resented the appointment and drove Mostian out. Later, another sheriff, Humphrey Willis, was driven out of Donegal at the start of Tyrone's Rebellion in the 1590s.
Mostian was a strong supporter of Perrot, who called him “my man.” He held the rank of captain in the Irish Army and also worked as a mercenary. He became involved in disputes among Ulster's Gaelic lords, being hired by Turlough O'Neill to reassert control over Hugh Maguire in Fermanagh. In 1588 Mostian returned to Donegal and, with his younger brother Hugh, raided across the area and even ransacked Donegal Abbey.
Scholars note that government-backed troublemakers like the Mostian brothers, Humphrey Willis, and John Connill helped push many loyal Donegal figures toward Tyrone's Rebellion. Ironically, William's brother Hugh later served as a mercenary for the rebel forces of Hugh Roe O'Donnell during the war.
This page was last edited on 2 February 2026, at 15:34 (CET).