Henry Fitzsimon (Fitz Simon; 1566 or 1569 in Dublin – 29 November 1643 or 1645, probably at Kilkenny) was an Irish Jesuit controversialist.
"[citation needed] Having embraced Catholicism, he visited Rome and Flanders, where in 1592, he "elected to militate under the Jesuits' standard, because they do most impugn the impiety of heretics".
Keeping chiefly to Dublin and Drogheda, he reconciled Protestants, and persistently challenged the chief Anglican divines.
At the outbreak of the Thirty Years War in 1620, he served as chaplain to the Irish soldiers in the imperial army, and published a diary of his experiences.
[citation needed] He was under sentence of death, from which he escaped in the winter of 1641 to the Wicklow Mountains, and (possibly) died in Kilkenny.