The Lord Lieutenant of Ireland (also known as the Viceroy or in the Middle Ages as the Lord Deputy) was the head of England's (pre-1707) or Britain's (post 1707) administration in Ireland.

The office was originally the central focus of English/British administration in Ireland under the Lordship of Ireland (1171-1541), the Kingdom of Ireland (1541-1800) and the United Kingdom of Great Britain and Ireland (1801-1922). As the name suggests, the holder was in effect the King's representative; the word viceroy comes from the french vice roi or deputy king. Though earlier Lords Deputy had been Irish noblemen, from the Middle Ages, with the very odd exception, only English or British noblemen were appointed to the office.

The official residence of the Lord Lieutenant was the Viceregal Apartments in Dublin Castle. However from the late eighteenth century, the Lord Lieutenant lived for much of the year in the Viceregal Lodge (now Áras an Uachtaráin, the Irish presidential palace), a more private residence located in the Phoenix Park in Dublin. In later years, Lords Lieutenant only lived in the Castle during the 'Social Season' (early January to St. Patrick's Day (March 17), during which time they held social events; balls, drawing rooms, etc. Other summer or alternative residences used by Lord Lieutenant or Lords Deputy included Abbeyville in Kinsealy (now the home of former taoiseach Charles Haughey) and a Chapelizod House, in which the Lord Lieutenant lived while Dublin Castle was being rebuilt following a fire but which he left due to the building being haunted. Lords Lieutenant and earlier Lords Deputy sometimes also owned property in Ireland, in which they lived rather than in state residences. The Geraldine Lords Deputy, Gearoid Mór Fitzgerald[?] and Gearoid Óg Fitzgerald[?] being native Irish both lived in, among other locations, their castle in Maynooth[?], Co. Kildare. The Earl of Essex owned Durhamstown Castle[?] near Navan[?] in County Meath, a short distance from the residence of the Lord Bishop of Meath at Ardbraccan.

The Lord Lieutenant's government was not in any real way responsible to the Irish Parliament, prior to parliament's abolition thanks to the Act of Union passed in 1800. Nevertheless, he did hold a formal State Opening of Parliament[?], delivering his speech outlining his government policy programme from the throne on the dias in the Irish House of Lords[?].

By the mid 19th century, the Lord Lieutenant's role changed substantially. Though still the official representative of the sovereign, the day to day role of governing fell to the Chief Secretary for Ireland[?], who was in effect the prime minister of the British administration in Ireland. Many nineteenth century Lords Lieutenant were not even nominally members of the British Cabinet, while the supposedly more junior Chief Secretary usually was.

The office of Lord Lieutenant, like the English and British government in Ireland was generally unpopular with Irish nationalists, though it was supported with varying degrees of enthusiasm by the Irish unionist community. Some Lords Lieutenants did earn a measure of popularity in a personal capacity among nationalists. From the early nineteenth century, calls were made frequently for the abolition of the office and its replacement by a Secretary of State for Ireland. Though on one occasion, a Bill was even introduced by one government to make this change, the office survived right down until the end of British rule in Ireland.

Irish nationalists throughout the nineteenth and early twentieth centuries campaigned for a form of Irish self-government. Daniel O'Connell sought Repeal[?] of the Act of Union, with the re-establishment of a Kingdom of Ireland, while later nationalists like Charles Stewart Parnell sought a more moderate form of home rule[?]within the United Kingdom of Great Britain and Ireland. Both made clear however, that the office of Lord Lieutenant could not survive in a restructured system of Irish government.

The last of the four Home Rule bills, the Government of Ireland Act, 1920, did provide for the continuation of the office. The Act divided Ireland into two states, Northern Ireland and Southern Ireland. Two institutions were meant to join the two states; a Council of Ireland[?] (which was hoped would evolve into a working all-Ireland parliament) and the Lord Lieutenant who would be the nominal chief executive of both regimes, appointing both prime ministers and dissolving both parliaments. In fact only Northern Ireland functioned as a state, with Southern Ireland being replaced by the Irish Free State. The powers meant to have been possessed by the Lord Lieutenant were delegated by amendment to a new Governor of Northern Ireland[?], while the role of representative of the Crown in the Free State went to a new southern Governor-General. The Lord Lieutenantship as a result was abolished.

Lord Fitzalan was the last holder, with the office abolished in December1922.

By tradition the coat of arms of each Lord Lieutenant was displayed somewhere in the Chapel Royal in Dublin Castle; some were incorporated into stained glass windows, some carved into seating, etc. Dubliners noted that the last available space was taken by the last Lord Lieutenant, Viscount Fitzalan. Fitzalan was the first Roman Catholic appointed as a representative of the Crown since the Glorious Revolution that brought William and Mary to power in 1688.