The Great Seal of Ireland was the seal used until 1922 by the Dublin Castle administration to authenticate important state documents in Ireland, in the same manner as the Great Seal of the Realm in England. The Great Seal of Ireland was used from at least the 1220s in the Lordship of Ireland and the ensuing Kingdom of Ireland, and remained in use when the island became part of the United Kingdom of Great Britain and Ireland (1801–1922),[1] just as the Great Seal of Scotland remained in use after the Act of Union 1707. After 1922, the single Great Seal of Ireland was superseded by the separate Great Seal of the Irish Free State and Great Seal of Northern Ireland for the respective jurisdictions created by the partition of Ireland.
When the Union with Ireland took effect in 1801, and from that time onwards, the Great Seal was frequently described in Acts of Parliament as the Great Seal of the United Kingdom, but the old Great Seal of Ireland continued to be used for many documents relating solely to Ireland.