Bagenal (Bagnal(l)), Sir Henry (c.1556–1598), soldier, was born in England, eldest son of Sir Nicholas Bagenal (qv) and his wife Eleanor (née Griffith; d. 1573) of Penrhyn, north Wales. Henry apparently left Oxford without graduating and began service in Ireland under his father. When Sir Nicholas became chief commissioner of Ulster (1577), Henry was made his assistant, and was knighted in 1578. His experience included command of the rear of the government force defeated at Glenmalure, Co. Wicklow (August 1580); he also, as commander at Carrickfergus, Co. Antrim, led a force that was ambushed and forced to retire during operations against Rathlin Island (September 1584). In 1586, the year in which he became MP for Anglesey, Bagenal presented at court his Description and present state of Ulster (1586), which stressed the strategic dangers of the area, and the need to curtail the powers of the O'Neills and set up a presidency of Ulster, with himself in a position similar to that of Richard Bingham (qv) in Connacht. The queen found much of this acceptable, but the proposals were dropped after bitter and violent disputes between the Bagenals and their colleagues in the Irish administration.
Nonetheless, Henry returned to Ireland (1587) as deputy to his father; and on 24 October 1590 succeeded him as marshal of the army and became a member of the Irish council. The following year he succeeded him as chief commissioner for Ulster (18 May 1591), but the position lacked substance at a time when the London government was conciliatory towards the O'Neills. Within three months his sister Mabel (qv), against his will, had married Hugh O'Neill (qv), 2nd earl of Tyrone. Henry refused to pay the dowry, and though he and O'Neill cooperated in defeating Hugh Maguire (qv) in 1593, the earl eventually began direct conflict with the government by attacking Bagenal at Clontibret, Co. Monaghan (13 June 1595), and later laid waste Bagenal's estates near Newry. Subsequent campaigns centred on the relief and supply of English garrisons in Ulster. In 1598 Bagenal (who had successfully resupplied Armagh in 1596–7) led over 4,000 men to relieve the Blackwater fort near Armagh, and was defeated by O'Neill, O'Donnell, and Maguire at the Yellow Ford (14 August), losing his own life, nearly half his force, and in consequence the fort – a severe blow to government control of Ireland. His body may have been buried in St Patrick's church, Newry.
Bagenal married (a. September 1586) Eleanor(a) Savage of Cheshire, cousin of the 3rd earl of Rutland, and had (either with her or in later marriages) at least three sons and six daughters.