Stormont Castle is a baronial mansion on the Stormont Estate

Stormont Estate

The Stormont Estate is an estate east of Belfast in County Down, Northern Ireland. It is within the townland of Ballymiscaw. The Stormont Estate includes Northern Ireland's main government buildings, which are surrounded mainly by woodland....

 in east Belfast

Belfast

Belfast is the capital of and largest city in Northern Ireland. By population, it is the 14th biggest city in the United Kingdom and second biggest on the island of Ireland . It is the seat of the devolved government and legislative Northern Ireland Assembly...

 which is used as the main meeting place of the Northern Ireland Executive

Northern Ireland Executive

The Northern Ireland Executive is the executive arm of the Northern Ireland Assembly, the devolved legislature for Northern Ireland. It is answerable to the Assembly and was established according to the terms of the Northern Ireland Act 1998, which followed the Good Friday Agreement...

.

Between 1921 and 1972 it served as the official residence of the Prime Minister of Northern Ireland

Prime Minister of Northern Ireland

The Prime Minister of Northern Ireland was the de facto head of the Government of Northern Ireland. No such office was provided for in the Government of Ireland Act 1920. However the Lord Lieutenant, as with Governors-General in other Westminster Systems such as in Canada, chose to appoint someone...

. However a number of prime ministers chose to live at Stormont House

Stormont House

Stormont House is the headquarters of the Northern Ireland Office, it is situated in the Stormont Estate in Belfast in Northern Ireland....

, the official residence of the Speaker of the House of Commons of Northern Ireland

House of Commons of Northern Ireland

The House of Commons of Northern Ireland was the lower house of the Parliament of Northern Ireland created under the Government of Ireland Act 1920. The upper house in the bicameral parliament was called the Senate. It was abolished with the passing of the Northern Ireland Constitution Act...

, which was empty as a number of speakers had chosen to live in their own homes. It also served as the location of the Cabinet Room of the Government of Northern Ireland

Executive Committee of the Privy Council of Northern Ireland

The Executive Committee or the Executive Committee of the Privy Council of Northern Ireland was the government of Northern Ireland created under the Government of Ireland Act 1920. Generally known as either the Cabinet or the Government, the Executive Committee existed from 1922 to 1972...

 from 1921 to 1972.

Before devolution it served as the Belfast headquarters of the Secretary of State for Northern Ireland

Secretary of State for Northern Ireland

The Secretary of State for Northern Ireland, informally the Northern Ireland Secretary, is the principal secretary of state in the government of the United Kingdom with responsibilities for Northern Ireland. The Secretary of State is a Minister of the Crown who is accountable to the Parliament of...

, Northern Ireland Office

Northern Ireland Office

The Northern Ireland Office is a United Kingdom government department responsible for Northern Ireland affairs. The NIO is led by the Secretary of State for Northern Ireland, and is based in Northern Ireland at Stormont House.-Role:...

 Ministers and supporting officials. During the troubles it was also used by MI5

MI5

The Security Service, commonly known as MI5 , is the United Kingdom's internal counter-intelligence and security agency and is part of its core intelligence machinery alongside the Secret Intelligence Service focused on foreign threats, Government Communications Headquarters and the Defence...

officers.