The Kingdom of Ireland was a client state of England and then of Great Britain that existed from 1542 until 1800 on the island of Ireland. It was ruled by the monarchs of England and then of Great Britain in personal union with their other realms. The kingdom was administered from Dublin Castle by a viceroy appointed by the king or queen. Ireland had its own legislature, peerage, army, and state church. Although styled a kingdom, for most of its history it was a de facto dependency of England, later Great Britain; a status enshrined in Poynings' Law and the Declaratory Act of 1719.
The territory of the kingdom had formerly been a lordship ruled by the kings of England, founded in 1177 by King Henry II after the Anglo-Norman invasion of Ireland. By the 16th century, the area of English rule had shrunk greatly, and most of Ireland was held by Gaelic Irish principalitys and chiefdoms. In 1542, King Henry VIII of England was made King of Ireland. The English began establishing control over the island, which sparked the Desmond Rebellions and the Nine Years' War. It was completed in the early 17th century.