The Dublin Castle administration in Ireland was the government of Ireland under British rule from the twelfth century until 1922. Its chief executive was variously known as the Justicar , the Lord Deputy and, from the seventeenth century, the Lord Lieutenant of Ireland (also known as the Viceroy), who was both the English (pre-1707)/British government representative in Ireland and the personal representative in Ireland of the King.

By the nineteenth century the Lord Lieutenant had declined in importance vis-a-vis his chief aide, the Chief Secretary for Ireland. By the late nineteenth century the Lord Lieutenant might be, but was not always a member of the British cabinet, while the Chief Secretary invariably was.

Under the Government of Ireland Act, 1920 the Lord Lieutenant was scheduled to take up a new role, that of the King's representative to the two Irish states, Northern Ireland and Southern Ireland. However Southern Ireland never became a working reality and was replaced by the Irish Free State in 1922. The lord lieutenancy was abolished, with his Northern role given to the Governor of Northern Ireland.

Other major offices in the Dublin Castle administration — Chief Secretary, Under Secretary, Lord Chancellor of Ireland, Attorney-General for Ireland (which was scheduled to have been replaced anyway by the Attorney-General for Southern Ireland under the Government of Ireland Act), and the Solicitor-General for Ireland — were all abolished. The Chief Secretary's office evolved to form the administrative basis for the new President of the Executive Council of the Irish Free State (prime minister), with the Under Secretary's administrative role becoming that of the new chief civil servant in the Irish government, the Secretary to the Executive Council.