Which years were the office of 'Lord Lieutenant of Ireland' applicable to?

The 'Lord Lieutenant of Ireland', or more formally 'Lord Lieutenant General and General Governor of Ireland', was the title of the chief governor of Ireland from the Williamite Wars of 1690 until the Partition of Ireland in 1922.

This spanned the Kingdom of Ireland (1541–1800) and the United Kingdom of Great Britain and Ireland (1801–1922). The office, under its various names, was often more generally known as the 'Viceroy', and his wife was known as the 'vicereine'.

The government of Ireland in practice was usually in the hands of the Lord Deputy up to the 17th century, and later of the Chief Secretary for Ireland.

It should be noted that although in the Middle Ages some Lords Deputy were Irish noblemen, only men from Great Britain, usually peers, were appointed to the office of Lord Lieutenant.

As Lord Lieutenant, he possessed a number of overlapping roles.

He was the representative of the King (the "viceroy"); the head of the executive in Ireland; (on occasion) a member of the English or British Cabinet; the fount of mercy, justice and patronage; (on occasion) commander-in-chief in Ireland, and also 'Grand Master of the Order of St. Patrick', (a British order of chivalry).

The 'Government of Ireland Act 1920' divided Ireland into two devolved entities inside the United Kingdom, Northern Ireland and Southern Ireland. The office of Lord Lieutenant of Ireland was abolished on 8 December 1922, two days after the Free State Constitution came into force.