His or Her Majesty's Privy Council in Ireland, commonly called the Privy Council of Ireland, Irish Privy Council, or in earlier centuries the Irish Council, was the institution within the Dublin Castle administration which exercised formal executive power in conjunction with the chief governor of Ireland, who was viceroy of the British monarch. The council evolved in the Lordship of Ireland on the model of the Privy Council of England; as the English council advised the king in person, so the Irish council advised the viceroy, who in medieval times was a powerful Lord Deputy. In the early modern period the council gained more influence at the expense of the viceroy, but in the 18th century lost influence to the Parliament of Ireland. In the post-1800 United Kingdom of Great Britain and Ireland, the Irish Privy Council and viceroy Lord Lieutenant had formal and ceremonial power, while policy formulation rested with a Chief Secretary directly answerable to the British cabinet. The council comprised senior public servants, judges, and parliamentarians, and eminent men appointed for knowledge of public affairs or as a civic honour.

Role As in England, the medieval unitary king's council evolved into distinct bodies, the smallest being the privy council, of senior advisors to the king (or, in Ireland's case, to the king's representative). Others were the great council, which evolved into the Parliament of Ireland, and the afforced council, an ad-hoc body of intermediate size.

The privy council played a leading role in directing the Tudor conquest of Ireland. It established and delegated to Presidencies in Munster and in Connaught, while directly supervising Leinster. Although the chief governor was appointed by the monarch under the Great Seal of England, a 1542 statute legalised the existing practice of an interim Lord Justice being elected by a meeting of the Irish council summoned by the Lord Chancellor of Ireland,34 Hen. 8 sess. 2 c. 1 as when William Drury was elected in 1579 between Henry Sidney's recall and Lord Grey's arrival.Hutchinson 2014 p.670 Charles I ordered the Lord Deputy to reform the "negligent meeting" of the privy council's committees. The Act of Explanation 1665 empowered the viceroy and council to override the royal charters of municipal corporations; the resulting "New Rules", which governed many major towns from 1672 until the Municipal Corporations (Ireland) Act 1840, allowed the council to veto the corporation's choice of mayor. This power was controversially used in Dublin in 1711–1714 to keep out Whigs, and in Cork in 1835 to keep out an Orangeman. The 1665 act also established a commission to resolve doubts over the Act of Settlement 1662; when the commission found further ambiguities in the 1665 act's terms of reference, it applied to the "Lord Lieutenant and Council" to resolve them.

Poynings' Law (1495) gave the Irish Privy Council a leading role in the legislative process. Before the council summoned each new Parliament (with a general election to the Commons) it had to submit the Parliament's bills to the Privy Council of England for approval as "causes and considerations" for the summons. Initially, all bills were by the Irish council, and the Commons and Lords could pass or reject, but not amend them. By the 18th century, a legal fiction arose where Parliament debated "heads of a bill" and petitioned the council to introduce it; the council could still amend or reject these "heads". Private bills were always initiated by the council until the Williamite revolution. The council gradually stopped initiating any bills beyond two "causes and considerations" bills, one of which was always a money bill, to which the Commons objected as violating its control of supply. The Patriot Party defeated the 1768 "Privy Council Money Bill", heralding an increase in parliamentary sovereignty which culminated in the Constitution of 1782, which removed the Irish Privy Council from the legislative process. (The British Privy Council retained the right to veto Irish bills, but not to amend them.)

Orders in Council were issued by the chief governor with the advice and consent of the Privy Council. From Elizabeth to Charles I, the Irish council filled the legislative gap during long intervals between Irish parliaments by passing "Acts of State", justified on grounds similar to those latterly used for Charles' Personal Rule. The governor could issue proclamations without the council on routine matters, but on important policy questions needed the council's agreement. The 1724 defeat of Wood's halfpence came after the Irish privy council sided with the Irish parliament in opposition to the British government and refused to intercede between parliament and the Lord Lieutenant, Lord Carteret.

The Irish council developed a judicial role later than the Privy Council of England, with the Court of Castle Chamber sitting in Dublin Castle from 1571 to 1641.

Privy Councillors had a right of audience with the viceroy, and many men were anxious to become members purely for this access and took little or no part in council business. Charles II's 1679 plan to reduce the number to 20 or 30 was not acted on. By the eighteenth century, there were over 100 councillors, few of whom usually attended meetings. Nevertheless, the viceroy informally consulted an inner circle before the formal council meetings, in order to expedite decision-making. In Great Britain a similar process led to the evolution of this inner circle or "cabinet" into the de facto government while the full privy council became a ceremonial body. Ireland's dependency and lack of responsible government prevented such a definitive division there. The oath of office for senior positions in the administration was taken at a council meeting. Latterly such offices as Vice-Treasurer of Ireland were sinecures whose holders might secure a private act of the British parliament allowing them to take the oath in Britain to save the bother of travelling to Dublin.See e.g. descriptions in Statute Law Revision Act 2009 Schedule 2 Part 3 of: 1 Geo. 1 St. 2 c. 39P; 3 Geo.1 c. 17P; 10 Geo. 1 c. 23P; 10 Geo. 1 c. 24P; 15 Geo. 2 c. 27P; 18 Geo. 2 c. 5P; 19 Geo. 2 c. 18P; 19 Geo. 2 c. 27P.

Although the Acts of Union 1800 abolished the Kingdom of Ireland and its parliament, its Privy Council (like the Lord Lieutenant) was retained, alternatives —abolishing the Irish council or merging it with the British one— receiving little consideration. In 1801 Lord Pelham, a former Chief Secretary for Ireland, became British Home Secretary and assumed that his office now extended to Ireland, but viceroy Philip Yorke, 3rd Earl of Hardwicke insisted that the silence of the 1800 acts regarding the Irish council implied that its assent remained obligatory for effecting government orders. Ireland under the Union had some government bodies answerable to the viceroy and Council and others which were divisions of Whitehall departments; however, a lack of collegiality prevented the Irish council becoming a rival power centre. In 1850 the First Russell ministry proposed to abolish the Lord Lieutenant and transfer some of his statutory functions to Privy Council of Ireland. Opposing this, Thomas Chisholm Anstey said, "The Privy Council of Ireland, like that of England, though the chief council for purposes of State, he regretted to say, was never summoned unless on holyday occasions, its duties having been usurped by the Cabinet Council, a body unknown to the common law."

In 1852 the Privy Council Office was merged into the Chief Secretary's Office. Latterly the council's executive role was merely formal and ceremonial. Of ten meetings held from August 1886 to January 1887, attendance ranged from four (including three Lords Justices) to ten (including the Lord Lieutenant). There was controversy over the proclamations issued by the council under the Criminal Law and Procedure (Ireland) Act 1887, since among the signatories were senior judges who might hear appeals against sentences handed down under the act. Sir Michael Morris, the Lord Chief Justice of Ireland, stated that in his 20 years attending council meetings, no "matter of policy" was discussed.

In the 19th century, petitions to the Privy Council against decisions of various administrative bodies were referred to committees of councillors with legal experience. Most committees were ad hoc, but there were statutory "judicial committees" (comprising current or former senior judges) relating to the Encumbered Estates' Court (1849–58) and Local Government (Ireland) Act 1898. Other committees heard appeals under the Tramways and Public Companies (Ireland) Act 1883, Educational Endowments (Ireland) Act 1885, Labourers (Ireland) Act 1885, and Irish Education Acts 1892 and 1893.McDowell 1976 pp. 106–107 The Veterinary Department of the Irish Privy Council, established 1866–72, was "most peculiarly constituted", having no corresponding committee of the council; it became the Veterinary Branch of the Department of Agriculture and Technical Instruction upon the latter's 1900 establishment.; Cattle Disease (Ireland) Amendment Act 1872 , preamble; The Privy Council's Irish Universities Committee was established in 1908 to hear petitions relating to the National University of Ireland (NUI) and Queen's University Belfast (QUB).

Supersession Although the Government of Ireland Act 1920 provided for the partition of Ireland into Northern Ireland and Southern Ireland, it had some all-island institutions, retaining the Privy Council, of which the northern and southern governments would technically be executive committees. Accordingly, the members of the first Executive Committee for Northern Ireland, the Craigavon ministry, were sworn of the Privy Council of Ireland in May 1921 immediately before Lord Lieutenant Viscount FitzAlan appointed them to their ministries. The 64 Southern Senators included eight elected by Privy Councillors from among their membership. Government of Ireland Act 1920 s.13 and Second Schedule, Part III; If the Southern Commons was inquorate, the Lord Lieutenant could replace the Southern Parliament with a committee of Privy Councillors, a provision dubbed "Crown Colony government". Government of Ireland Act 1920 s.72(1) ; ; During the Anglo-Irish War the 1921 Southern election was won by abstentionsts of Sinn Féin, and the "Crown Colony" provision seemed likely to be invoked, but a truce was agreed leading to the Anglo-Irish Treaty. The British initially hoped the resulting Provisional Government could be appointed under the "Crown Colony" provision, but realised ministers from Sinn Féin would refuse the Privy Council oath, and instead the Irish Free State (Agreement) Act 1922 replaced much of the 1920 act as regards Southern Ireland.